tree-optimization/114749 - reset partial vector decision for no-SLP retry

The following makes sure to reset LOOP_VINFO_USING_PARTIAL_VECTORS_P
to its default of false when re-trying without SLP as otherwise
analysis may run into bogus asserts.

	PR tree-optimization/114749
	* tree-vect-loop.cc (vect_analyze_loop_2): Reset
	LOOP_VINFO_USING_PARTIAL_VECTORS_P when re-trying without SLP.

gcc/tree-vect-loop.cc

@@ -3400,6 +3400,7 @@ again:
   LOOP_VINFO_VERSIONING_THRESHOLD (loop_vinfo) = 0;
   LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo)
     = saved_can_use_partial_vectors_p;
+  LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo) = false;
 
   goto start_over;
 }