[mips][mips64r6] bc1[tf] are not available on MIPS32r6/MIPS64r6

Summary:
Also tightened up the acceptable condition operand for these instructions
on MIPS-I to MIPS-III. Support for $fcc[1-7] was added in MIPS-IV. Prior
to that only $fcc0 is acceptable.

We currently don't optimize (BEQZ (NOT $a), $target) and similar. It's
probably best to do this in InstCombine.

Depends on D4111

Reviewers: jkolek, zoran.jovanovic, vmedic

Reviewed By: vmedic

Differential Revision: http://reviews.llvm.org/D4112