pan/mdg: Emit fcsel when beneficial

pan/mdg: Emit fcsel when beneficial

If there are floating point modifiers, we emit fcsel instead of icsel
(and likewise if integer modifiers, icsel instead of fcsel) to minimize
redundant instructions.

total instructions in shared programs: 3628 -> 3626 (-0.06%)
instructions in affected programs: 139 -> 137 (-1.44%)
helped: 2
HURT: 0

total bundles in shared programs: 1886 -> 1885 (-0.05%)
bundles in affected programs: 19 -> 18 (-5.26%)
helped: 1
HURT: 0

total quadwords in shared programs: 3319 -> 3317 (-0.06%)
quadwords in affected programs: 127 -> 125 (-1.57%)
helped: 2
HURT: 0

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5123>