tree-optimization/125686 - missing bits in PR125646 fix

The following patches up synth_lshift_by_additions and
apply_binop_and_append_stmt to set the correct vector type on
the pattern stmt generated.

	PR tree-optimization/125686
	* tree-vect-patterns.cc (synth_lshift_by_additions): Specify
	pattern vector type.
	(apply_binop_and_append_stmt): Likewise.
	(vect_synth_mult_by_constant): Adjust.

(cherry picked from commit de7756c90f3bebdf02492842ec355d7e18745e7b)