Added support for DPP instruction in assembler for VOP1 and VOP2 formats. Added tests for assembler.
ToDo:
- VOP2bInst:
- vcc is considered as operand
- AsmMatcher doesn't apply mnemonic aliases when parsing operands
- v_mac_f32
- v_nop
- disable instructions with 64-bit operands
- change dpp_ctrl assembler representation to conform sp3
Use IsImmTy(...) here and below.