[5/n] PR85694: Remove dead WIDEN_SUM handling

[5/n] PR85694: Remove dead WIDEN_SUM handling

vect_recog_dot_prod_pattern and vect_recog_sad_pattern both checked
whether the statement passed in had already been recognised as a
WIDEN_SUM_EXPR pattern.  That isn't possible (any more?), since the
first recognised pattern wins, and since vect_recog_widen_sum_pattern
never matches a later statement than the one it's given.

2018-06-20  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-patterns.c (vect_recog_dot_prod_pattern): Remove
	redundant WIDEN_SUM_EXPR handling.
	(vect_recog_sad_pattern): Likewise.

From-SVN: r261788