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/Sinlinx_SinA31s_defconfig b/configs/Sinlinx_SinA31s_defconfig
index 54c975a..7f815a3 100644
--- a/configs/Sinlinx_SinA31s_defconfig
+++ b/configs/Sinlinx_SinA31s_defconfig
@@ -10,7 +10,6 @@
 CONFIG_USB2_VBUS_PIN=""
 CONFIG_DEFAULT_DEVICE_TREE="sun6i-a31s-sina31s"
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
-CONFIG_SYS_EXTRA_OPTIONS="SUNXI_GMAC"
 CONFIG_SPL=y
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
@@ -19,5 +18,6 @@
 # CONFIG_SPL_ISO_PARTITION is not set
 # CONFIG_SPL_EFI_PARTITION is not set
 CONFIG_ETH_DESIGNWARE=y
+CONFIG_SUN7I_GMAC=y
 CONFIG_AXP_DLDO1_VOLT=3300
 CONFIG_USB_EHCI_HCD=y