[NFC][ELF][AArch64][MTE] Don't duplicate addRelativeReloc call for MTE globals
This call to addRelativeReloc is the same as the one at the end of the
function, so skip the relrDyn code for this case and add the special
out-of-bounds handling code to the end of the function. This makes it
obvious where MTE globals differ in behaviour rather than having to
compare the two different implementations.
This also adds a comment documenting why relrDyn isn't used, and in it
highlights that it's probably safe to use relrDyn so long as the offset
is within the symbol's bounds.
Reviewers: pcc, kovdan01, MaskRay
Reviewed By: MaskRay
Pull Request: https://github.com/llvm/llvm-project/pull/171181