openmp: Fix up warnings on libgomp.info build

When building libgomp documentation, I see
makeinfo --split-size=5000000  -I ../../../libgomp/../gcc/doc/include -I ../../../libgomp -o libgomp.info ../../../libgomp/libgomp.texi
../../../libgomp/libgomp.texi:503: warning: node next `omp_get_default_device' in menu `omp_get_device_num' and in sectioning `omp_get_dynamic' differ
../../../libgomp/libgomp.texi:528: warning: node prev `omp_get_dynamic' in menu `omp_get_device_num' and in sectioning `omp_get_default_device' differ
../../../libgomp/libgomp.texi:560: warning: node next `omp_get_initial_device' in menu `omp_get_level' and in sectioning `omp_get_device_num' differ
../../../libgomp/libgomp.texi:587: warning: node next `omp_get_device_num' in menu `omp_get_dynamic' and in sectioning `omp_get_level' differ
../../../libgomp/libgomp.texi:587: warning: node prev `omp_get_device_num' in menu `omp_get_default_device' and in sectioning `omp_get_initial_device' differ
../../../libgomp/libgomp.texi:615: warning: node prev `omp_get_level' in menu `omp_get_initial_device' and in sectioning `omp_get_device_num' differ
warnings.  This patch fixes those.

2021-10-12  Jakub Jelinek  <jakub@redhat.com>

	* libgomp.texi (omp_get_device_num): Move @node before omp_get_dynamic
	to avoid makeinfo warnings.