pan/midgard/disasm: Fix printing 8-bit/16-bit masks

pan/midgard/disasm: Fix printing 8-bit/16-bit masks

The trick is realizing even with a destination override, the masks are encoded in the same mode as the
instruction itself, rather than stepping down. The override means that
the smaller type is used, but the mask is parsed as if it were the
higher type. Overriding down is down by printed by blinding doing this. Overriding up can be thought of as printing in the upper size, but shifting the alphabet to use the upper half, i.e. shifting xyzw to become abcd.

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