Add big endian support for MIPS in Liftoff.

Bug: v8:6600
Change-Id: Ibd90e7b6a8f0f826bd70ef489135cabcadeed7b0
Reviewed-on: https://chromium-review.googlesource.com/995457
Commit-Queue: Sreten Kovacevic <sreten.kovacevic@mips.com>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ivica Bogosavljevic <ivica.bogosavljevic@mips.com>
Cr-Commit-Position: refs/heads/master@{#52565}