net: fec: introduce fec_ptp_stop and use in probe fail path

commit 32cba57ba74be58589aeb4cb6496183e46a5e3e5 upstream.

This function frees resources and cancels delayed work item that
have been initialized in fec_ptp_init().

Use this to do proper error handling if something goes wrong in
probe function after fec_ptp_init has been called.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Fugang Duan <B38611@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[groeck: backport: context changes in .../fec_main.c]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>