net/af-xdp.c: maybe-uninitialized warning with gcov build on ubuntu2404

This is a false positive, fixed by explicitly initializing variable to NULL. Variable is always initialized during the for loop above, which is guaranteed to run since queues >= 1. This is correctly detected for normal builds, but not for gcov builds. In function ‘af_xdp_read_poll’, inlined from ‘net_init_af_xdp’ at ../net/af-xdp.c:546:5: ../net/af-xdp.c:78:10: error: ‘s’ may be used uninitialized [-Werror=maybe-uninitialized] 78 | if (s->read_poll != enable) { | ~^~~~~~~~~~~ ../net/af-xdp.c: In function ‘net_init_af_xdp’: ../net/af-xdp.c:461:17: note: ‘s’ was declared here 461 | AFXDPState *s; | Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com> Link: https://lore.kernel.org/qemu-devel/20260610192222.2709135-2-pierrick.bouvier@oss.qualcomm.com Signed-off-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>