msm: emac: Allow to program 1GB speed via ethtool

Currently ethtool don't allow to program 1GB link
speed. Apart from that it does not retain existing
speed if disabled autonegotiation.

Change-Id: I00e35af5738e1e30227971bcda1629183be00ebf
Signed-off-by: Alok Chauhan <alokc@codeaurora.org>