[mips] Correct jal expansion for local symbols in .local directives.

This patch corrects the behaviour of code such as:

   .local foo
   jal foo
foo:
to use the correct jal expansion when writing ELF files.

Patch by: Daniel Sanders

Reviewers: zoran.jovanovic, seanbruno, vkalintiris

Differential Revision: https://reviews.llvm.org/D24722

llvm-svn: 287918