Replace "driver" with "drivers" in the filepath to net_failover.c

Cc: Sridhar Samudrala <sridhar.samudrala@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Fixes: cfc80d9a ("net: Introduce net_failover driver")
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>