libgomp.fortran/omp_target_memset.f90 - Avoid implicit mapping by an uninit size...

libgomp.fortran/omp_target_memset.f90 - Avoid implicit mapping by an uninit size [PR122543]

In OpenMP, pointers are implicitly mapped - which means for Fortran that
their pointer target is also mapped. However, for uninitialized memory,
this means that some random pointee with some random amount of memory is
copied - in the good case, size == 0, but if not, odd things can happen.

Solution: Use 'fptr => null()' before the target mapping or - as done here -
declare the pointer inside the region.

libgomp/ChangeLog:

	PR libgomp/122543
	* testsuite/libgomp.fortran/omp_target_memset.f90: Move fptr inside
	the target to avoid implicit mapping of its uninit pointee.
	* testsuite/libgomp.fortran/omp_target_memset-2.f90: Likewise.