On Loongson 3A, MADD/MSUB instructions are actually fused MADD/MSUB and
they can cause failure in some of the tests. Since this optimization is
rarely used, and not used at all on MIPS64R6, MADD/MSUB instructions
are removed from the source base.

TEST=
BUG=

Change-Id: Ifbb5508a62731bb061f332864ffd1e210e97f963
Reviewed-on: https://chromium-review.googlesource.com/558066Reviewed-by: Ivica Bogosavljevic <ivica.bogosavljevic@imgtec.com>
Commit-Queue: Ivica Bogosavljevic <ivica.bogosavljevic@imgtec.com>
Cr-Commit-Position: refs/heads/master@{#46387}