pan/bi: Implement FMA/MOV without modifiers

pan/bi: Implement FMA/MOV without modifiers

We split off MOV from FMOV since the canonical move on Bifrost doesn't
accept modifiers. (We can still do fmov, but with something like add-0.)
This will also make copyprop a little nicer, I think. Anyway, the
non-modifier version we can implement as-is for FMA.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4276>