[TableGen] Predicate::operator== needs to compare the HwMode feature name in...

[TableGen] Predicate::operator== needs to compare the HwMode feature name in addition to the HwMode flag.

This was causing GenerateVariants to lose some variants since
HwMode is expanded first. We were mistakenly thinking the HwMode
predicate matched and finding the variant was isomorphic to a
pattern in another HwMode and discarding it.

Found while investigating it if would be better to generate
variants before expanding HwModes to improve RISCV build time.
I noticed an increase in the number of Opc_MorphNodeTo in the table
which indicated that the number of patterns had changed.