fortran: Apply if clause to all sub-constructs in combined OpenMP constructs

fortran: Apply if clause to all sub-constructs in combined OpenMP constructs

The unmodified 'if' clause should be applied to all the sub-constructs that
accept an 'if' clause in a combined OpenMP construct, and not just to the
'parallel' sub-construct.

2020-06-25  Kwok Cheung Yeung  <kcy@codesourcery.com>

gcc/fortran/

	* trans-openmp.c (gfc_split_omp_clauses): Add if clause
	to target and simd sub-constructs.

gcc/testsuite/

	* gfortran.dg/gomp/combined-if.f90: New.

Reviewed-by: Jakub Jelinek <jakub@redhat.com>