panfrost: Tiled to linear layout conversion

panfrost: Tiled to linear layout conversion

Tiling is expensive, so this patch converts textures that appear to be
used for streaming to a linear layout.

Performance of mpv is significantly improved, with software-decoded
1080p mp4 playback on RK3288 going from 30fps to 50fps when testing
with `--untimed --no-audio`.

To keep things simple, conversion only happens when updating the whole
texture and no mipmapping is used.

v2: Make it clear that the heuristic doesn't rely on a texture being
uninitialized, since layout switching code can get confusing (Alyssa).

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4628>