DAGCombiner: Use correct value type for checking legality of BR_CC v3

LegalizeDAG.cpp uses the value of the comparison operands when checking
the legality of BR_CC, so DAGCombiner should do the same.

v2:
  - Expand more BR_CC value types for NVPTX

v3:
  - Expand correct BR_CC value types for Hexagon, Mips, and XCore.

llvm-svn: 176694