panfrost: Overhaul tilebuffer allocations

panfrost: Overhaul tilebuffer allocations

Based on the colour buffers in use, we need to select a tile size
allowing either 128-bits of storage per pixel or 512-bits. Based on the
size chosen, we scale the offsets into the tilebuffer. Likewise, we need
to calculate offsets based on bpp (with special cases) rather than
picking an average case.

Fixes regressions that otherwise would be caused by the next commit.

v2: Fix colour clears (Icecream95).

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5858>