staging: fsl-dpaa2/ethsw: fix memory leak of switchdev_work

In the default event case switchdev_work is being leaked because
nothing is queued for work. Fix this by kfree'ing switchdev_work
before returning NOTIFY_DONE.

Addresses-Coverity: ("Resource leak")
Fixes: 44baaa43 ("staging: fsl-dpaa2/ethsw: Add Freescale DPAA2 Ethernet Switch driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>