[X32][CET] Fix handling of indirect branches

As X32 uses 32-bit pointers without having 32-bit indirect branch
instructions, we need to fix up indirect branches by extending the
branch targets to 64 bits. This was already done for BRIND but not yet
for NT_BRIND. The same logic works for both, so this applies that
existing logic to NT_BRIND as well.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D101499