testsuite: Fix up depobj-3.c test on i686-linux [PR112724]

While I've posted a patch to handle EXCESS_PRECISION_EXPR in C/C++
pretty printing, still we'd need to handle
(a + (float)5)
and
(float)(((long double)a) + (long double)5)
and possibly
(float)(((double)a) + (double)5)
too for s390?, so the following patch just uses -fexcess-precision=fast,
so that the expression is always the same.

2024-03-22  Jakub Jelinek  <jakub@redhat.com>

	PR c++/112724
	* c-c++-common/gomp/depobj-3.c: Add -fexcess-precision=fast as
	dg-additional-options.

gcc/testsuite/c-c++-common/gomp/depobj-3.c

+/* { dg-additional-options "-fexcess-precision=fast" } */
+
 typedef struct __attribute__((__aligned__ (sizeof (void *)))) omp_depend_t {
   char __omp_depend_t__[2 * sizeof (void *)];
 } omp_depend_t;