Add 'dg-do run' to 'libgomp.fortran/use_device_ptr-optional-3.f90' [PR94848]

Fix-up for r279858/commit f760c0c7 "Fortran]
OpenMP/OpenACC – fix more issues with OPTIONAL".

With offloading enabled, we then saw:

    PASS: libgomp.fortran/use_device_ptr-optional-3.f90   -O0  (test for excess errors)
    PASS: libgomp.fortran/use_device_ptr-optional-3.f90   -O0  execution test
    PASS: libgomp.fortran/use_device_ptr-optional-3.f90   -O1  (test for excess errors)
    PASS: libgomp.fortran/use_device_ptr-optional-3.f90   -O1  execution test
    FAIL: libgomp.fortran/use_device_ptr-optional-3.f90   -O2  (test for excess errors)
    UNRESOLVED: libgomp.fortran/use_device_ptr-optional-3.f90   -O2  compilation failed to produce executable
    FAIL: libgomp.fortran/use_device_ptr-optional-3.f90   -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions  (test for excess errors)
    UNRESOLVED: libgomp.fortran/use_device_ptr-optional-3.f90   -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions  compilation failed to produce executable
    FAIL: libgomp.fortran/use_device_ptr-optional-3.f90   -O3 -g  (test for excess errors)
    UNRESOLVED: libgomp.fortran/use_device_ptr-optional-3.f90   -O3 -g  compilation failed to produce executable
    FAIL: libgomp.fortran/use_device_ptr-optional-3.f90   -Os  (test for excess errors)
    UNRESOLVED: libgomp.fortran/use_device_ptr-optional-3.f90   -Os  compilation failed to produce executable

 ... due to:

    /tmp/cciVc43I.o:(.gnu.offload_vars+0x10): undefined reference to `A.12.4064'
    [...]

..., but after the recent PR94848, PR95551 changes, that problem is now gone.

	libgomp/
	PR lto/94848
	* testsuite/libgomp.fortran/use_device_ptr-optional-3.f90: Add
	'dg-do run'.

(cherry picked from commit 5864930754f63e2dcef9606f2514ae20e80f436e)

libgomp/testsuite/libgomp.fortran/use_device_ptr-optional-3.f90

+! { dg-do run }
 ! Check whether absent optional arguments are properly
 ! handled with use_device_{addr,ptr}.
 program main