sunxi: sina33: Enable the eMMC

The SinA33 has an 4GB Toshiba eMMC connected to the MMC2 controller.
Enable it.
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: NChen-Yu Tsai <wens@csie.org>
Reviewed-by: NHans de Goede <hdegoede@redhat.com>

configs/Sinlinx_SinA33_defconfig

@@ -4,6 +4,7 @@ CONFIG_MACH_SUN8I_A33=y
 CONFIG_DRAM_CLK=552
 CONFIG_DRAM_ZQ=15291
 CONFIG_MMC0_CD_PIN="PB4"
+CONFIG_MMC_SUNXI_SLOT_EXTRA=2
 CONFIG_USB0_ID_DET="PH8"
 CONFIG_DEFAULT_DEVICE_TREE="sun8i-a33-sinlinx-sina33"
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set