[X86] Don't emit R_X86_64_[REX_]GOTPCRELX for a GOT load with an offset

clang may produce `movl x@GOTPCREL+4(%rip), %eax` when loading the high
32 bits of the address of a global variable in -fpic/-fpie mode.

If assembled by GNU as, the fixup emits R_X86_64_GOTPCRELX with an addend != -4.
The instruction loads from the GOT entry with an offset and thus it is incorrect
to relax the instruction.

This patch does not emit a relaxable relocation for a GOT load with an offset
because R_X86_64_[REX_]GOTPCRELX do not make sense for instructions which cannot
be relaxed.  The result is good enough for LLD to work. GNU ld relaxes
mov+GOTPCREL as well, but it suppresses the relaxation if addend != -4.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D92114