MLK-11307 net: fec: disable timer interrupt when link down and suspend

There exists one issue in Android environment when do power key on/off
test that cause system hang. Because suspend function disable enet all
clocks while timer interrupt comming that introduces registers access.
When link down and suspend, the timer interrupt is not necessary
to enable, so disable it.

Signed-off-by: Fugang Duan <B38611@freescale.com>
Tested-by: Fugang Duan <B38611@freescale.com>
Tested-by: Chen Guoyin <B07211@freescale.com>
Tested-by: Zhu Wenbo <B52619@freescale.com>
(cherry picked from commit: 048f62891bc4936991fd58dbaf4a606a30282404)