net: mvpp2.c: Enable 10G support for port 0 (SFI)

net: mvpp2.c: Enable 10G support for port 0 (SFI)

This patch fixes some remaining issues in the mvpp2 driver for the 10GB
support on port 0. These changes are:

- Incorrect PCS configuration
- Skip PHY configuration when no PHY is connected
- Skip GMAC configurations if 10G SFI mode set

Signed-off-by: Stefan Chulski <stefanc@marvell.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Kostya Porotchkin <kostap@marvell.com>
Cc: Nadav Haklai <nadavh@marvell.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>