[SVE] Fix crashes with inline assembly

All the crashes found compiling inline assembly are fixed in this
patch by changing AArch64TargetLowering::getRegForInlineAsmConstraint
to be more resilient to mismatched value and register types. For
example, it makes no sense to request a predicate register for
a nxv2i64 type and so on.

Tests have been added here:

  test/CodeGen/AArch64/inline-asm-constraints-bad-sve.ll

Differential Revision: https://reviews.llvm.org/D92554