[ELF][MIPS] Ignore incorrect version definition index for _gp_disp symbol

MIPS BFD linker puts _gp_disp symbol into DSO files and assigns zero
version definition index to it. This value means 'unversioned local
symbol' while _gp_disp is a section global symbol. We have to handle
this bug in the LLD because BFD linker is used for building MIPS
toolchain libraries.

Differential revision: https://reviews.llvm.org/D42486

llvm-svn: 324467