Torture testing: 'libgomp.fortran/use_device_ptr-optional-2.f90'

Fix-up for commit a2c26c50 (r278046) "Fortran]
Support absent optional args with use_device_{ptr,addr}".

	libgomp/
	* testsuite/libgomp.fortran/use_device_ptr-optional-2.f90: Add
	'dg-do run'.