net/failsafe: fix duplicate event registration
net/failsafe: fix duplicate event registration

When the fail-safe device is reconfigured, it attempts to register
again for the sub-devices LSC and RMV events.

Prevent an event registration if it is already done.

Fixes: 598fb8aec6f6 ("net/failsafe: support device removal")
Cc: stable@dpdk.org

Signed-off-by: Matan Azrad <6969f5f553ad7652679a585a85d7321babc90464@mellanox.com>
Acked-by: Gaetan Rivet <a6b9f1aecd7707f01344f211143eb3bcaeb0c5c3@6wind.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk