freedreno: Allow UBWC on textures with multiple mipmap levels.

freedreno: Allow UBWC on textures with multiple mipmap levels.

This is a backport of Jonathan Marek's UBWC work on turnip to GL.

Performance highlights from our trace set (320 frames sampled)
traces/glmark2/texture-texture-filter=mipmap.rdc:    +9.1% +/-   2.2%
traces/android/trex.rdc:                             +8.7% +/-   0.4%
traces/glmark2/desktop-effect=shadow:windows=4.rdc:  +4.2% +/-   2.5%

Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3059>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3059>