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.
LegalizeDAG: Respect the result of TLI.getBooleanContents() when expanding SETCC
R600: Set BooleanContents to ZeroOrNegativeOneBooleanContent

Reviewed-by: Christian König <christian.koenig@amd.com>
R600: Change operation action from Custom to Expand for SETCC

Reviewed-by: Christian König <christian.koenig@amd.com>
R600: Change operation action from Custom to Expand for BR_CC

Reviewed-by: Christian König <christian.koenig@amd.com>
R600: Improve custom lowering of select_cc

Two changes:
1. Prefer SET* instructions when possible
2. Handle the CND*_INT case with floating-point args

Reviewed-by: Christian König <christian.koenig@amd.com>
R600: Optimize another selectcc case

fold selectcc (selectcc x, y, a, b, cc), b, a, b, setne ->
     selectcc x, y, a, b, cc

Reviewed-by: Christian König <christian.koenig@amd.com>