anv/hasvk/drirc: change anv_assume_full_subgroups to have subgroup size
MR changes anv_assume_full_subgroups to specify max subgroup size. We set max as 16 for UnrealEngine5.1.
anv/hasvk/drirc: change anv_assume_full_subgroups to have subgroup size
drirc: setup anv_assume_full_subgroups=16 for UnrealEngine5.1