freedreno: batch cache doesn't hold a ref to batch

freedreno: batch cache doesn't hold a ref to batch

The cache doesn't hold a (strong) reference to the batch.  So we
shouldn't be trying to drop a reference, as that leads to:

   #0  0x0000ffffbecb37a0 in raise () from /lib64/libc.so.6
   #1  0x0000ffffbeca159c in abort () from /lib64/libc.so.6
   #2  0x0000ffffbecacf48 in __assert_fail_base () from /lib64/libc.so.6
   #3  0x0000ffffbecacfa8 in __assert_fail () from /lib64/libc.so.6
   #4  0x0000ffffbd28def0 in pipe_reference_described (ptr=0x4f47130, reference=0x0, get_desc=0xffffbd2e0f08 <__fd_batch_describe>) at ../src/gallium/auxiliary/util/u_inlines.h:88
   #5  0x0000ffffbd28e188 in fd_batch_reference_locked (ptr=0x4f40de0, batch=0x0) at ../src/gallium/drivers/freedreno/freedreno_batch.h:258
   #6  0x0000ffffbd28e9a8 in fd_bc_invalidate_resource (rsc=0x4f40ca0, destroy=true) at ../src/gallium/drivers/freedreno/freedreno_batch_cache.c:244
   #7  0x0000ffffbd293778 in fd_resource_destroy (pscreen=0xedc170, prsc=0x4f40ca0) at ../src/gallium/drivers/freedreno/freedreno_resource.c:644
   #8  0x0000ffffbd922674 in u_transfer_helper_resource_destroy (pscreen=0xedc170, prsc=0x4f40ca0) at ../src/gallium/auxiliary/util/u_transfer_helper.c:144
   #9  0x0000ffffbd29527c in pipe_resource_reference (ptr=0x4f455d8, tex=0x0) at ../src/gallium/auxiliary/util/u_inlines.h:144
   #10 0x0000ffffbd29548c in fd_surface_destroy (pctx=0x1012720, psurf=0x4f455d0) at ../src/gallium/drivers/freedreno/freedreno_surface.c:78
   #11 0x0000ffffbd1f9c48 in pipe_surface_reference (ptr=0x4f471d0, surf=0x0) at ../src/gallium/auxiliary/util/u_inlines.h:113
   #12 0x0000ffffbd1f9ef4 in util_copy_framebuffer_state (dst=0x4f471c8, src=0x0) at ../src/gallium/auxiliary/util/u_framebuffer.c:114
   #13 0x0000ffffbd2e0e30 in __fd_batch_destroy (batch=0x4f47130) at ../src/gallium/drivers/freedreno/freedreno_batch.c:225
   #14 0x0000ffffbd28e1b0 in fd_batch_reference_locked (ptr=0xfffffffff010, batch=0x0) at ../src/gallium/drivers/freedreno/freedreno_batch.h:262
   #15 0x0000ffffbd28e6b0 in fd_bc_invalidate_context (ctx=0x1012720) at ../src/gallium/drivers/freedreno/freedreno_batch_cache.c:190
   #16 0x0000ffffbd2e2b6c in fd_context_destroy (pctx=0x1012720) at ../src/gallium/drivers/freedreno/freedreno_context.c:139
   #17 0x0000ffffbd2c3280 in fd5_context_destroy (pctx=0x1012720) at ../src/gallium/drivers/freedreno/a5xx/fd5_context.c:56
   #18 0x0000ffffbd5b7a8c in st_destroy_context_priv (st=0xfd72f0, destroy_pipe=true) at ../src/mesa/state_tracker/st_context.c:281

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