Require equal type sizes for vectorised calls

Require equal type sizes for vectorised calls

As explained in the comment, vectorizable_call needs more work to
support mixtures of sizes.  This avoids testsuite fallout for
later SVE patches.

2019-11-14  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-stmts.c (vectorizable_call): Require the types
	to have the same size.

From-SVN: r278239