[ARM/AArch64] Ensure valid vector element types for interleaved accesses

This patch refactors and strengthens the type checks performed for interleaved
accesses. The primary functional change is to ensure that the interleaved
accesses have valid element types. The added test cases previously failed
because the element type is f128.

Differential Revision: https://reviews.llvm.org/D31817

llvm-svn: 299864