freedreno/a6xx: Fix UBWC mipmap sizing.

The HW requires a log2 width/height of the level 0 meta_* size in the
descriptors, making it pretty clear that UBWC mipmapping is all
power-of-two sized.  Fixes a bunch of failures in the upcoming unit UBWC
layout unit tests.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4931>
2 files changed