[Mips Assembler] Add alias definitions for jal

Mips assembler allows following to be used as aliased instructions:
jal $rs for jalr $rs
jal $rd,$rd for jalr $rd,$rs

This patch provides alias definitions in td files and test cases to show the usage.

Contributer: Vladimir Medic


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178304 91177308-0d34-0410-b5e6-96231b3b80d8