panfrost: Implement opportunistic AFBC

panfrost: Implement opportunistic AFBC

Rather than hardcoding a BO layout at creation-time, we implement the
ability to hint layouts at various points in a BO's lifetime,
potentially reallocating and switching layouts if it's heuristically
deemed useful to do so.

In this patch, we add a simple hinting implementation, opportunistically
compressing FBOs.

Support is hidden behind PAN_MESA_DEBUG=afbc as the implementation is
incomplete (software access to AFBC is unimplemented at the moment) and
therefore would regress significantly.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>