slp: reject non-multiple of 2 laned SLP trees (PR99825)

slp: reject non-multiple of 2 laned SLP trees (PR99825)

TWO_OPERANDS allows any order or number of combinations of + and - operations
but the pattern matcher only supports pairs of operations.

This patch has the pattern matcher for complex numbers reject SLP trees where
the lanes are not a multiple of 2.

gcc/ChangeLog:

	PR tree-optimization/99825
	* tree-vect-slp-patterns.c (vect_check_evenodd_blend):
	Reject non-mult 2 lanes.

gcc/testsuite/ChangeLog:

	PR tree-optimization/99825
	* gfortran.dg/vect/pr99825.f90: New test.