[NDS32] Define and rename some GPR-specific stuff.

[NDS32] Define and rename some GPR-specific stuff.

	* config/nds32/nds32.c (nds32_function_arg): Define and rename some
	GPR-specific stuff.
	(nds32_function_arg_advance): Likewise.
	(nds32_init_cumulative_args): Likewise.
	* config/nds32/nds32.h (NDS32_MAX_GPR_REGS_FOR_ARGS): Define.
	(NDS32_FIRST_GPR_REGNUM): Define.
	(NDS32_LAST_GPR_REGNUM): Define.
	(NDS32_AVAILABLE_REGNUM_FOR_GPR_ARG): Define.
	(NDS32_ARG_PASS_IN_REG_P): Use NDS32_MAX_GPR_REGS_FOR_ARGS.
	(FUNCTION_ARG_REGNO_P): Use NDS32_MAX_GPR_REGS_FOR_ARGS.
	(machine_function): Use GRP-specific stuff.

From-SVN: r214859