net: fec: fix system hang during suspend/resume

1. During normal suspend (WoL not enabled) process, system has posibility
to hang. The root cause is TXF interrupt coming after clocks disabled,
system hang when accessing registers from interrupt handler. To fix this
issue, disable all interrupts when system suspend.

2. System also has posibility to hang with WoL enabled during suspend,
after entering stop mode, then magic pattern coming after clocks
disabled, system will be waked up, and interrupt handler will be called,
system hang when access registers. To fix this issue, disable wakeup
irq in .suspend(), and enable it in .resume().

Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>