gfni: change immediate mode arguments in tests to be in [0, 255]
gfni: change immediate mode arguments in tests to be in [0, 255]

GCC checks that the value is in [0, 255] instead of just accepting
any value and only using the least significant 8 bits like ICC and
clang do.

nemequ/simde,nemequ/simde,nemequ/simde