This follows on from similar changes a couple of months ago and
is needed when general modes have variable size.

2017-10-23  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* tree-vect-loop.c (vect_create_epilog_for_reduction): Use
	SCALAR_TYPE_MODE instead of TYPE_MODE.

From-SVN: r254002