[mips][mips64r6] Add addiupc, aluipc, and auipc

Summary:
No support for symbols in place of the immediate yet since it requires new
relocations.

Depends on D3671

Reviewers: jkolek, zoran.jovanovic, vmedic

Reviewed By: vmedic

Differential Revision: http://reviews.llvm.org/D3689

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208858 91177308-0d34-0410-b5e6-96231b3b80d8