Fix return value, using -EAGAIN instead of 0 when the callback is busy
and using -ENOENT instead of 0 when the callback is not found.
Fixes: a753e53d517b ("eal: add device event monitor framework")
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Acked-by: Jeff Guo <jia.guo@intel.com>
Acked-by: David Marchand <david.marchand@redhat.com>