mips64: Add tests that cover Cavium-specific load indexed instructions

Tests for lhux, lwux, and lbx for Cavium Octeon II.

Patch by Zahid Anwar, with changes.

Related to Bugzilla issue 326444.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13786 a5019735-40e9-0310-863c-91ae7b9d1cf9