AArch64: Macrofusion: Split features, add missing combinations.

AArch64InstrInfo::shouldScheduleAdjacent() determines whether two
instruction can benefit from macroop fusion on apple CPUs. The list
turned out to be incomplete:
- the "rr" variants of the instructions were missing
- even the "rs" variants can have shift value == 0 and behave like the
  "rr" variants

This also splits the MacropFusion target feature into
ArithmeticBccFusion and ArithmeticCbzFusion.

Differential Revision: https://reviews.llvm.org/D25142

llvm-svn: 283243