[AVX-512] Update lowering for gather/scatter prefetch intrinsics to match the...

[AVX-512] Update lowering for gather/scatter prefetch intrinsics to match the immediate encodings the frontend uses based on the _MM_HINT_T0/T1 constant values in clang's headers.

Our _MM_HINT_T0/T1 constant values are 3/2 which matches gcc, but not icc or Intel documentation. Interestingly gcc had this same bug on their implementation of the gather/scatter builtins at one point too.

Fixes PR32411.

llvm-svn: 299234