[mips] Make whitespace in disassembler tests more consistent. NFC.

[mips] Make whitespace in disassembler tests more consistent. NFC.

The tests for the ISA's should now be approximately diffable. That is, the
output of 'diff valid-mips1.txt valid-mips2.txt' should be emit the lines
for instructions that were added/removed to/from MIPS-I by MIPS-II. This
doesn't work perfectly at the moment due to ordering differences but it
should be close.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226408 91177308-0d34-0410-b5e6-96231b3b80d8