Move builtin functions implementation to nds32-intrinsic.c module.

Move builtin functions implementation to nds32-intrinsic.c module.

gcc/
	* config/nds32/nds32.c
	(nds32_expand_builtin_null_ftype_reg): Move to ...
	(nds32_expand_builtin_reg_ftype_imm): Move to ...
	(nds32_expand_builtin_null_ftype_reg_imm): Move to ...
	(nds32_init_builtins): Move implementation to ...
	(nds32_expand_builtin): Move implementation to ...
	* config/nds32/nds32-intrinsic.c: ... here.
	* config/nds32/nds32-protos.h (nds32_init_builtins_impl): Declare.
	(nds32_expand_builtin_impl): Declare.

Co-Authored-By: Kito Cheng <kito@0xlab.org>
Co-Authored-By: Monk Chiang <sh.chiang04@gmail.com>
From-SVN: r212282