[68/77] Use scalar_mode for is_int_mode/is_float_mode pairs

This patch uses scalar_mode for code that operates only on MODE_INT
and MODE_FLOAT.

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* omp-expand.c (expand_omp_atomic): Use is_int_mode, is_float_mode
	and scalar_mode.
	* tree-vect-stmts.c (get_vectype_for_scalar_type_and_size): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251519