msm: emac: Add wake lock for link detection/un-detection

Add wake lock support in EMAC driver. EMAC driver should
not go into suspend when Ethernet link is connected to
avoid transfer to fail.  For this reason wake lock is
acquired when Ethernet link is detected and it will hold
the system to go into suspend as long as link is connected.
Once Ethernet link is disconnected then EMAC driver will
release the wake lock and allow system to go into suspend.

Change-Id: I6ffafbd085608d0a96d96fc5b87695a9ff5198ce
Signed-off-by: Alok Chauhan <alokc@codeaurora.org>