Move some helper functions of predicates and constraints to nds32-predicates.c module.

Move some helper functions of predicates and constraints to nds32-predicates.c module.

gcc/
	* config/nds32/nds32.c
	(nds32_consecutive_registers_load_store_p): Move to ...
	(nds32_valid_multiple_load_store): Move to ...
	(nds32_valid_stack_push_pop): Move to ...
	(nds32_can_use_bclr_p): Move to ...
	(nds32_can_use_bset_p): Move to ...
	(nds32_can_use_btgl_p): Move to ...
	(nds32_can_use_bitci_p): Move to ...
	* config/nds32/nds32-predicates.c: ... here.

Co-Authored-By: Kito Cheng <kito@0xlab.org>
Co-Authored-By: Monk Chiang <sh.chiang04@gmail.com>
From-SVN: r212283