sunxi: Convert SUNXI_EMAC to Kconfig

Convert the SUNXI_EMAC config to Kconfig. Remove it from SYS_EXTRA_OPTIONS
from many sunxi defconfig and renamed it into SUN4I_EMAC to not confuse it
with SUN8I_EMAC.

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/configs/Cubieboard_defconfig b/configs/Cubieboard_defconfig
index e1d1f1f..78fd4a2 100644
--- a/configs/Cubieboard_defconfig
+++ b/configs/Cubieboard_defconfig
@@ -6,7 +6,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="sun4i-a10-cubieboard"
 CONFIG_AHCI=y
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
-CONFIG_SYS_EXTRA_OPTIONS="SUNXI_EMAC,SATAPWR=SUNXI_GPB(8)"
+CONFIG_SYS_EXTRA_OPTIONS="SATAPWR=SUNXI_GPB(8)"
 CONFIG_SPL=y
 CONFIG_SPL_I2C_SUPPORT=y
 # CONFIG_CMD_IMLS is not set
@@ -15,4 +15,5 @@
 # CONFIG_SPL_DOS_PARTITION is not set
 # CONFIG_SPL_ISO_PARTITION is not set
 # CONFIG_SPL_EFI_PARTITION is not set
+CONFIG_SUN4I_EMAC=y
 CONFIG_USB_EHCI_HCD=y