anv/icl: Don't set float blend optimization bit in CACHE_MODE_SS

anv/icl: Don't set float blend optimization bit in CACHE_MODE_SS

CACHE_MODE_SS is not listed in gfxspecs table for user mode
non-privileged registers. So, making any changes from Mesa
will do nothing. Kernel is already setting this bit in
CACHE_MODE_SS register which is saved/restored to/from
the HW context image.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>