This change adds usxgmii support in UNIPHY0.
Earlier it was supported up to PSGMII with 4 ports.
With these changes,
UNIPHY0 supports either of the 2 modes mentioned below.
1. PSGMII with 4 ports
2. USXGMII with 1 port
Change-Id: Ic4ca62e3ef74d275cda92d86b459d204ee4325ed
Signed-off-by: Vandhiadevan Karunamoorthy <quic_vkarunam@quicinc.com>