net: macb: save/restore the remaining registers and features

SAMA5D2 SoC has a suspend mode where SoC's power is cut off. Due to this
the registers content is lost after a suspend/resume cycle. The current
suspend/resume implementation covers some of these registers. However
there are few which were not treated (e.g. SCRT2 and USRIO). Apart
from this, netdev features are not restored. Treat these issues.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>