sunxi: Move SUNXI_GMAC to Kconfig

Move the SUNXI_GMAC config option to Kconfig, remove it
from SYS_EXTRA_OPTIONS and rename it into SUN7I_GMAC.

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/configs/Sinovoip_BPI_M2_defconfig b/configs/Sinovoip_BPI_M2_defconfig
index dbff234..d123fad 100644
--- a/configs/Sinovoip_BPI_M2_defconfig
+++ b/configs/Sinovoip_BPI_M2_defconfig
@@ -6,7 +6,7 @@
 CONFIG_USB2_VBUS_PIN=""
 CONFIG_DEFAULT_DEVICE_TREE="sun6i-a31s-sinovoip-bpi-m2"
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
-CONFIG_SYS_EXTRA_OPTIONS="SUNXI_GMAC,RGMII"
+CONFIG_SYS_EXTRA_OPTIONS="RGMII"
 CONFIG_SPL=y
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
@@ -15,6 +15,7 @@
 # CONFIG_SPL_ISO_PARTITION is not set
 # CONFIG_SPL_EFI_PARTITION is not set
 CONFIG_ETH_DESIGNWARE=y
+CONFIG_SUN7I_GMAC=y
 CONFIG_AXP_ALDO1_VOLT=3300
 CONFIG_AXP_ALDO2_VOLT=1800
 CONFIG_AXP_DLDO1_VOLT=3000