[mips] Refine the condition for when to use CALL16 vs a GOT displacement.

Borrow from the logic for 'jal' in MipsAsmParser::processInstruction
and add the extra condition of bypassing CALL16 if the destination symbol
is an ELF symbol with STB_LOCAL binding.

Patch by: John Baldwin

Reviewers: sdardis

Differential Revision: https://reviews.llvm.org/D33999

llvm-svn: 306387