[5/7] Move the fix for PR65518

[5/7] Move the fix for PR65518

This patch moves the fix for PR65518 to the code that checks whether
load-and-permute operations are supported.   If the group size is
greater than the vectorisation factor, it would still be possible
to fall back to elementwise loads (as for strided groups) rather
than fail vectorisation entirely.

Tested on aarch64-linux-gnu and x86_64-linux-gnu.

gcc/
	* tree-vectorizer.h (vect_grouped_load_supported): Add a
	single_element_p parameter.
	* tree-vect-data-refs.c (vect_grouped_load_supported): Likewise.
	Check the PR65518 case here rather than in vectorizable_load.
	* tree-vect-loop.c (vect_analyze_loop_2): Update call accordignly.
	* tree-vect-stmts.c (vectorizable_load): Likewise.

From-SVN: r238037