freedreno: limit tiling to PIPE_BIND_SAMPLER_VIEW

freedreno: limit tiling to PIPE_BIND_SAMPLER_VIEW

1ce5d757d04 dropped this limit.. which is probably the right thing to
do.  But it results in an extra tiled->linear blit for glReadPixels()
(ie. dEQP/piglit) which is hitting some intermittent corruption (looks
like cache) on a6xx, causing a lot of spurious fails.

Since we are getting close to 19.0 branchpoint, re-instate this limit
for now, until the blitter problems are resolved.

Fixes: 1ce5d757d04 freedreno: core buffer modifier support
Signed-off-by: Rob Clark <robdclark@gmail.com>