[vect] Only change base alignment if more restrictive

[vect] Only change base alignment if more restrictive

This patch makes sure ensure_base_align only changes alignment if the new
alignment is more restrictive.  It already did this if we were dealing with
symbols, but it now does it for all types of declarations.

gcc/ChangeLog:
2019-10-21  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	* tree-vect-stmts (ensure_base_align): Only change alignment if new
	alignment is more restrictive.

From-SVN: r277238