panfrost: Clean-up one-argument passing quirk

panfrost: Clean-up one-argument passing quirk

Most Midgard instructions take two-arguments logically; there are always
two arguments at the assembly level. For the few instructions that take
only a single argument, generally the second argument slot is unused,
with a zero inline constant occupying the space. fmov/imov are the
exception, where the first argument is filled with r24 and the logical
argument is in the second slot.

Previously, these constraints were handled by a delicate, buggy series
of hacks. This commit removes these hacks. Instead, we look at the
logical number of arguments (from NIR), switching between two argument
and one-argument-one-zero style. We then introduce a quirk for the
flipped style, which applies to fmov/imov.

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