freedreno/a6xx: separate stencil restore/resolve fixes

freedreno/a6xx: separate stencil restore/resolve fixes

Previously we'd use format/etc from the primary (z32) buffer for the
stencil (s8), due to confusion about rsc vs psurf.  Rework this to drop
extra arg and push down handling of separate stencil case (and make sure
we take the fmt from the right place).

This doesn't completely fix separate-stencil, but at least it avoids the
GPU scribbling over random other cmdstream buffers and causing a bunch
of bogus fails in dEQP.

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