arch: added missing MIPS HI/LO register defs (#749)

Author: Tazdevil971

Diff for: src/arch.rs

@@ -581,6 +581,9 @@ registers!(MIPS, {
     F29 = (61, "$f29"),
     F30 = (62, "$f30"),
     F31 = (63, "$f31"),
+
+    HI = (64, "$hi"),
+    LO = (65, "$lo"),
 },
 aliases {
     ZERO = (0, "$zero"),