[mips] Add tests for t0-t3 for N32/N64

These are aliases of t4-t7 and are provided for compatibility with both the
original ABI documentation (using t4-t7) and GNU As (using t0-t3)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204797 91177308-0d34-0410-b5e6-96231b3b80d8