tree-optimization/106403 - fix ICE with VN of .STORE_LANES

While .STORE_LANES is not supported by the recent VN patch we were
still accessing the stored value and valueizing it - but
internal_fn_stored_value_index does not support .STORE_LANES and
we failed to honor that case.  Fixed by simply moving the affected
code below the check for the actual supported internal functions.

	PR tree-optimization/106403
	* tree-ssa-sccvn.cc (vn_reference_lookup_3): Move stored
	value valueization after check for IFN_MASKED_STORE or
	IFN_LEN_STORE.