mode-switching: Pass the set of live registers to the after hook

mode-switching: Pass the set of live registers to the after hook

This patch passes the set of live hard registers to the after hook,
like the previous one did for the needed hook.

gcc/
	* target.def (mode_switching.after): Add a regs_live parameter.
	* doc/tm.texi: Regenerate.
	* config/epiphany/epiphany-protos.h (epiphany_mode_after): Update
	accordingly.
	* config/epiphany/epiphany.cc (epiphany_mode_needed): Likewise.
	(epiphany_mode_after): Likewise.
	* config/i386/i386.cc (ix86_mode_after): Likewise.
	* config/riscv/riscv.cc (riscv_mode_after): Likewise.
	* config/sh/sh.cc (sh_mode_after): Likewise.
	* mode-switching.cc (optimize_mode_switching): Likewise.