panfrost: Rename tiler fields per tiler research

panfrost: Rename tiler fields per tiler research

Following the research into Midgard's hierarchical tiling
infrastructure, we now understand (in broad stokes) the purpose of each
tiler field in the MFBD. Additionally, we understand more of the tiling
fields in the SFBD and in Bifrost's structures, although this knowledge
is still incomplete.

Update the names, decoder, and comments to reflect this new
understanding.

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