arm64: defconfig: enable stmmac and realtek PHY as modules

Some Amlogic GXBB boards use the stmmac ethernet driver.  Also, enable
the realtek PHY used on meson-gxbb-odroidc2.  The micrel PHY used on the
meson-gxbb-p20x boards is already enabled.
Signed-off-by: NKevin Hilman <khilman@baylibre.com>

arch/arm64/configs/defconfig

@@ -128,6 +128,8 @@ CONFIG_SKY2=y
 CONFIG_RAVB=y
 CONFIG_SMC91X=y
 CONFIG_SMSC911X=y
+CONFIG_STMMAC_ETH=m
+CONFIG_REALTEK_PHY=m
 CONFIG_MICREL_PHY=y
 CONFIG_USB_PEGASUS=m
 CONFIG_USB_RTL8150=m