Move ISR impelentation to nds32-isr.c module.

Move ISR impelentation to nds32-isr.c module.

gcc/
	* config/nds32/nds32.c (nds32_emit_section_head_template): Move to ...
	(nds32_emit_section_tail_template): Move to ...
	(nds32_emit_isr_jmptbl_section): Move to ...
	(nds32_emit_isr_vector_section): Move to ...
	(nds32_emit_isr_reset_conten): Move to ...
	(nds32_check_isr_attrs_conflict): Move to ...
	(nds32_construct_isr_vectors_information): Move to ...
	(nds32_asm_file_start): Move implementation to ...
	(nds32_asm_file_end): Move implementation to ...
	* config/nds32/nds32-isr.c: ... here.
	* config/nds32/nds32-protos.h
	(nds32_check_isr_attrs_conflict): Declare.
	(nds32_construct_isr_vectors_information): Declare.
	(nds32_asm_file_start_for_isr): Declare.
	(nds32_asm_file_end_for_isr): Declare.

Co-Authored-By: Kito Cheng <kito@0xlab.org>
Co-Authored-By: Monk Chiang <sh.chiang04@gmail.com>
From-SVN: r212281