[x86] add missing tests for fcmp ueq/one

Somehow, the codegen logic for these sequences has gone completely untested
until now (note the 2 compare instructions generated per test).

There's also an *Intel* AVX optimization opportunity exposed in these cases
and the existing tests. Intel's (but not AMD's) AVX spec shows that extra FP
predicates were added, so a single comparison should always be sufficient,
and operand commutation should never be necessary.

llvm-svn: 272397