tree-optimization/102905 - restore re-align load for alignment peeling

tree-optimization/102905 - restore re-align load for alignment peeling

Previous refactoring made the possibility of considering re-aligned
loads for unlimited cost model alignment peeling difficult so I
ditched that.  Later refactoring made it easily possible again so
the following patch re-instantiates this which should fix the
observed regression on powerpc with altivec.

2021-10-25  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102905
	* tree-vect-data-refs.c (vect_enhance_data_refs_alignment):
	Use vect_supportable_dr_alignment again to determine whether
	an access is supported when not aligned.