uboot-oxnas: re-add IC+ phy driver

uboot-oxnas: re-add IC+ phy driver

KD20 got an IC+ phy, without the driver the phy is not properly
initialized resulting in ethernet not working unless being already
initialized by the vendor loader.

upstream commit 368b4d2b49bbbf379d9334747fbbd2aaaafe4356
drivers: net: remove dead drivers
removed icplus.c due to the lack of in-tree users.
Partially revert that commit adding back the IC+ driver.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43508 3c298f89-4303-0410-b956-a3cf2f4a3e73