Correct trivial programming errors.

2013-03-04  Jeremy Bennett <jeremy.bennett@embecosm.com>

	* linux-arc-low.c (arc_fill_regset): Use regbuf->scratch.ret
	rather than regbuf->reg.
	(arc_store_regset): Typo - use supply_register_by_name rather than
	collect_register_by_name for stop_pc.