gallivm: add TGSI bit arithmetic opcodes support
Add ctlz & bitrev wrapper to bit arithmetic functions. Add TGSI_OPCODE_BFI, TGSI_OPCODE_POPC, TGSI_OPCODE_LSB, TGSI_OPCODE_IMSB, TGSI_OPCODE_UMSB, TGSI_OPCODE_IBFE, TGSI_OPCODE_UBFE, TGSI_OPCODE_BREV support.