icorem6: Use CONFIG_DM_ETH support

Use CONFIG_DM_ETH and remove board_eth_init code
from board files.

Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/arch/arm/cpu/armv7/mx6/Kconfig b/arch/arm/cpu/armv7/mx6/Kconfig
index eefe629..544f9af 100644
--- a/arch/arm/cpu/armv7/mx6/Kconfig
+++ b/arch/arm/cpu/armv7/mx6/Kconfig
@@ -126,6 +126,7 @@
 	select MX6QDL
 	select OF_CONTROL
 	select DM
+	select DM_ETH
 	select DM_GPIO
 	select DM_MMC
 	select DM_THERMAL