[mips] Fix disassembly of [ls][wd]c[23], cache, and pref                          
                                                                                  
Fixes PR21015, and PR20993.                                                       
                                                                                  
Patch by Jun Koi



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218745 91177308-0d34-0410-b5e6-96231b3b80d8