[AVX] Implement EnforceSmallerThan for mixed int/fp type lists. This

[AVX] Implement EnforceSmallerThan for mixed int/fp type lists.  This
makes type checking for extract_subvector and insert_subvector more
robust and will allow stricter typechecking of more patterns in the
future.

This change handles int and fp as disjoint sets so that it will
enforce integer types to be smaller than the largest integer type and
fp types to be smaller than the largest fp type.  There is no attempt
to check type sizes across the int/fp sets.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124672 91177308-0d34-0410-b5e6-96231b3b80d8