The CL adds optimizations to MipsCtz and MipsPopcnt for mips32 and to
Mips64Ctz, Mips64Dctz, Mips64Popcnt and Mips64Dpopcnt for mips64 in
code generator.

BUG=

Change-Id: I080d4eca6b8521c3d01d727b883f3efa9876b7a1
Reviewed-on: https://chromium-review.googlesource.com/563197Reviewed-by: Ivica Bogosavljevic <ivica.bogosavljevic@imgtec.com>
Commit-Queue: Miran Karić <Miran.Karic@imgtec.com>
Cr-Commit-Position: refs/heads/master@{#46496}