freedreno: rework blit API

freedreno: rework blit API

First step to unify the way fd5 and fd6 blitter works.  Currently a6xx
bypasses the blit API in order to also accelerate resource_copy_region()

But this approach can lead to infinite recursion:

  #0  fd_alloc_staging (ctx=0x5555936480, rsc=0x7fac485f90, level=0, box=0x7fbab29220) at ../src/gallium/drivers/freedreno/freedreno_resource.c:291
  #1  0x0000007fbdebed04 in fd_resource_transfer_map (pctx=0x5555936480, prsc=0x7fac485f90, level=0, usage=258, box=0x7fbab29220, pptrans=0x7fbab29240) at ../src/gallium/drivers/freedreno/freedreno_resource.c:479
  #2  0x0000007fbe5c5068 in u_transfer_helper_transfer_map (pctx=0x5555936480, prsc=0x7fac485f90, level=0, usage=258, box=0x7fbab29220, pptrans=0x7fbab29240) at ../src/gallium/auxiliary/util/u_transfer_helper.c:243
  #3  0x0000007fbde2dcb8 in util_resource_copy_region (pipe=0x5555936480, dst=0x7fac485f90, dst_level=0, dst_x=0, dst_y=0, dst_z=0, src=0x7fac47c780, src_level=0, src_box_in=0x7fbab2945c) at ../src/gallium/auxiliary/util/u_surface.c:350
  #4  0x0000007fbdf2282c in fd_resource_copy_region (pctx=0x5555936480, dst=0x7fac485f90, dst_level=0, dstx=0, dsty=0, dstz=0, src=0x7fac47c780, src_level=0, src_box=0x7fbab2945c) at ../src/gallium/drivers/freedreno/freedreno_blitter.c:173
  #5  0x0000007fbdf085d4 in fd6_resource_copy_region (pctx=0x5555936480, dst=0x7fac485f90, dst_level=0, dstx=0, dsty=0, dstz=0, src=0x7fac47c780, src_level=0, src_box=0x7fbab2945c) at ../src/gallium/drivers/freedreno/a6xx/fd6_blitter.c:587
  #6  0x0000007fbde2f3d0 in util_try_blit_via_copy_region (ctx=0x5555936480, blit=0x7fbab29430) at ../src/gallium/auxiliary/util/u_surface.c:864
  #7  0x0000007fbdec02c4 in fd_blit (pctx=0x5555936480, blit_info=0x7fbab29588) at ../src/gallium/drivers/freedreno/freedreno_resource.c:993
  #8  0x0000007fbdf08408 in fd6_blit (pctx=0x5555936480, info=0x7fbab29588) at ../src/gallium/drivers/freedreno/a6xx/fd6_blitter.c:546
  #9  0x0000007fbdebdc74 in do_blit (ctx=0x5555936480, blit=0x7fbab29588, fallback=false) at ../src/gallium/drivers/freedreno/freedreno_resource.c:129
  #10 0x0000007fbdebe58c in fd_blit_from_staging (ctx=0x5555936480, trans=0x7fac47b7e8) at ../src/gallium/drivers/freedreno/freedreno_resource.c:326
  #11 0x0000007fbdebea38 in fd_resource_transfer_unmap (pctx=0x5555936480, ptrans=0x7fac47b7e8) at ../src/gallium/drivers/freedreno/freedreno_resource.c:416
  #12 0x0000007fbe5c5c68 in u_transfer_helper_transfer_unmap (pctx=0x5555936480, ptrans=0x7fac47b7e8) at ../src/gallium/auxiliary/util/u_transfer_helper.c:516
  #13 0x0000007fbde2de24 in util_resource_copy_region (pipe=0x5555936480, dst=0x7fac485f90, dst_level=0, dst_x=0, dst_y=0, dst_z=0, src=0x7fac47b8e0, src_level=0, src_box_in=0x7fbab2997c) at ../src/gallium/auxiliary/util/u_surface.c:376
  #14 0x0000007fbdf2282c in fd_resource_copy_region (pctx=0x5555936480, dst=0x7fac485f90, dst_level=0, dstx=0, dsty=0, dstz=0, src=0x7fac47b8e0, src_level=0, src_box=0x7fbab2997c) at ../src/gallium/drivers/freedreno/freedreno_blitter.c:173
  #15 0x0000007fbdf085d4 in fd6_resource_copy_region (pctx=0x5555936480, dst=0x7fac485f90, dst_level=0, dstx=0, dsty=0, dstz=0, src=0x7fac47b8e0, src_level=0, src_box=0x7fbab2997c) at ../src/gallium/drivers/freedreno/a6xx/fd6_blitter.c:587
  ...

Instead rework the API to push the fallback back to core code, so that
we can rework resource_copy_region() to have it's own fallback path,
and then finally convert fd6 over to work in the same way.

This also makes ctx->blit() optional, and cleans up some unnecessary
callers.

Signed-off-by: Rob Clark <robdclark@gmail.com>