Use shift instructions to eliminate redundant compare/test instructions on the H8

Use shift instructions to eliminate redundant compare/test instructions on the H8

gcc/ChangeLog

	* config/h8300/h8300-protos.h (compute_a_shift_cc): Accept
	additional argument for the code.
	* config/h8300/h8300.c (compute_a_shift_cc): Accept additional
	argument for the code.  Just return if the ZN bits are useful or
	not rather than the old style CC_* enums.
	* config/h8300/shiftrotate.md (shiftqi_noscratch): Move before
	more generic shiftqi patterns.
	(shifthi_noscratch, shiftsi_noscratch): Similarly.
	(shiftqi_noscratch_set_flags): New pattern.
	(shifthi_noscratch_set_flags, shiftsi_noscratch_set_flags): Likewise.