nir: allow sat on all float destination types
nir: allow sat on all float destination types

With the introduction of fp64 and fp16 to nir, there are now a bunch of
float types running around. A F1 2015 shader ends up with an i2f.sat
operation, which has a nir_type_float32 destination. Allow sat on all
the float destination types.

Signed-off-by: Ilia Mirkin <bcbbb7aa705ec3a5fc5824c01a845186c3d62fca@alum.mit.edu>
Cc: "12.0" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Reviewed-by: Jason Ekstrand <68c46a606457643eab92053c1c05574abb26f861@jlekstrand.net>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler