Currently SIMD integer comparison ops are implemented using Lt/Le, this is
sub-optimal on Intel, because all compares are done using pcmpgt(d/w/b) that
clobber the destination register, and will need additional instructions to
when using Lt/Le as the base implementation. This CL proposes moving to Gt/Ge
as the underlying implementation as this will only require swapping operands
on MIPS and is consistent with x86/ARM instructions.

BUG=v8:6020

R=bbudge@chromium.org, bmeurer@chromium.org, bradnelson@chromium.org

Review-Url: https://codereview.chromium.org/2874403002
Cr-Commit-Position: refs/heads/master@{#45440}