[ELF][MIPS] Fix TLS GOT entries for local symbols in shared libraries

Summary:
Previously LLD would not add any dynamic relocations and write a module
index of 1 which is not correct for the shared library case.
This can happen when a thread-local global variable is marked as local with
a version script. With this change I am now able to link all of the FreeBSD
base system for MIPS64 with LLD.

Differential Revision: https://reviews.llvm.org/D48002

llvm-svn: 334483