MIPS: Implement HRor

This also fixes differentiation between the SRL and ROTR
instructions in the disassembler.

Change-Id: Ie19697f8d6ea8fa4e338adde3e3cf8e4a0383eae
diff --git a/disassembler/disassembler_mips.cc b/disassembler/disassembler_mips.cc
index ee7b21c..f922687 100644
--- a/disassembler/disassembler_mips.cc
+++ b/disassembler/disassembler_mips.cc
@@ -56,7 +56,7 @@
   // R-type instructions.
   { kRTypeMask, 0, "sll", "DTA", },
   // 0, 1, movci
-  { kRTypeMask, 2, "srl", "DTA", },
+  { kRTypeMask | (0x1f << 21), 2, "srl", "DTA", },
   { kRTypeMask, 3, "sra", "DTA", },
   { kRTypeMask | (0x1f << 6), 4, "sllv", "DTS", },
   { kRTypeMask | (0x1f << 6), 6, "srlv", "DTS", },