freedreno: handle case of shadowing current render target

freedreno: handle case of shadowing current render target

If you have a sequence where there is a single buffer associated with
the current render target, and then you end up shadowing it on the 3d
pipe (u_blitter), because of how we swap the new shadow and rsc before
the back-blit, you could end up confusing things into thinking that
the blitters framebuffer state is the same as the current framebuffer
state.

Re-organizing the sequence to swap after the blit is complicated when
also having to deal with CPU memcpy blit path, and the batch/rsc
accounting.  So instead just detect this case and flush if we need to.

Fixes:
dEQP-GLES31.functional.stencil_texturing.render.depth24_stencil8_clear
dEQP-GLES31.functional.stencil_texturing.render.depth24_stencil8_draw

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6434>