Add additional missing Allegrex CPU instructions

Allegrex supports some MIPS32 and MIPS32r2 instructions (albeit with
some encoding differences) such as bit manipulation (ins/ext) and MLA
(madd/msub).  It also features some new instructions like wsbw and
min/max or device-specific ones such as mfic.

Signed-off-by: David Guillen Fandos <david@davidgf.net>