ARM: shmobile: lager: Set ethernet PHY LED mode

The Lager board uses the ethernet PHY LED0 as a link signal connected to
the ethernet controller. Specify the corresponding LED mode for the PHY.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>