Add Vitesse 8601 support to TSEC driver

Add phy_info for Vitesse VSC8601.
Add config option, CFG_VSC8601_SKEWFIX, to enable RGMII skew timing compensation.

Signed-off-by: Tor Krill <tor@excito.com>
Reviewed-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>