net: ravb: Move the update of ndev->features to ravb_set_features()

Commit c2da9408 ("ravb: Add Rx checksum offload support for GbEth")
introduced support for setting GbEth features. With this the IP-specific
features update functions update the ndev->features individually.

Next commits add runtime PM support for the ravb driver. The runtime PM
implementation will enable/disable the IP clocks on
the ravb_open()/ravb_close() functions. Accessing the IP registers with
clocks disabled blocks the system.

The ravb_set_features() function could be executed when the Ethernet
interface is closed so we need to ensure we don't access IP registers while
the interface is down when runtime PM support will be in place.

For these, move the update of ndev->features to ravb_set_features(). In
this way we update the ndev->features only when the IP-specific features
set function returns success and we can avoid code duplication when
introducing runtime PM registers protection.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>