C-SKY: Separate FRAME_POINTER_REGNUM into FRAME_POINTER_REGNUM and HARD_FRAME_POINTER...

C-SKY: Separate FRAME_POINTER_REGNUM into FRAME_POINTER_REGNUM and HARD_FRAME_POINTER_REGNUM.

gcc/ChangeLog:

	* config/csky/csky.h (FRAME_POINTER_REGNUM): Use
	HARD_FRAME_POINTER_REGNUM and FRAME_POINTER_REGNUM instead of
	the signle definition. The signle definition may not work well
	at simplify_subreg_regno().
	(HARD_FRAME_POINTER_REGNUM): New.
	(ELIMINABLE_REGS): Add for HARD_FRAME_POINTER_REGNUM.
	* config/csky/csky.c (get_csky_live_regs, csky_can_eliminate,
	csky_initial_elimination_offset, csky_expand_prologue,
	csky_expand_epilogue): Add for HARD_FRAME_POINTER_REGNUM.