[Sema] Use isSVESizelessBuiltinType instead of isSizelessBuiltinType to prevent crashing on RISC-V.

These 2 spots are protecting calls to SVE specific functions. If RISC-V
sizeless types end up in there we trigger assertions.

Use the more specific isSVESizelessBuiltinType() to avoid letting
RISC-V vectors through.

Reviewed By: asb, c-rhodes

Differential Revision: https://reviews.llvm.org/D144772