ARM: shmobile: koelsch: Conditionally select MICREL_PHY

The koelsch board uses has an SH ethernet controller which uses a Micrel
phy. Select MICREL_PHY for koelsch if SH_ETH is enabled to make use of the
Micrel-specific phy driver rather than relying on the generic phy driver.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>