panfrost: Identify Bifrost texture format swizzle

panfrost: Identify Bifrost texture format swizzle

We don't force w=1 for Bifrost textures. We already compose this into
the swizzle as necessary, so we can just ignore this field I think. But
let's identify it so we don't forget what it is.

The blob uses it to force w=1 for <= 3-channel formats (0x10), as well
as a flag to swap r/b for BGRA (0x4). There are probably other flags
here but it doesn't.. really matter to us.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5232>