ARM: shmobile: koelsch: Set ethernet PHY LED mode

The Koelsch 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>