fec: Simplify the PM related hooks

Get rid of the CONFIG_PM_SLEEP ifdef by annotating the suspend/resume functions
with '__maybe_unused' in order to keep the code simpler and shorter.

While at it, declare the suspend/resume functions in a single line.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>