MIPS64: Optimize simulator.

MIPS64: Optimize simulator.

Port 09f41681ef83fe9e9d79748e2a60f16b70d5934c

Original commit message:
The patch decreases the calls of huge switch instructions making the
DecodeType*() functions to work in one phase and optimizing
Instruction::InstructionType(). Speed gain in release full check is
about 33% (6:13 s -> 4:09 s) and in optdebug full test is about 50%
(12:29 -> 6:17)

BUG=

Review URL: https://codereview.chromium.org/1356693002

Cr-Commit-Position: refs/heads/master@{#30824}