ARM: multi_v7_defconfig: enable the Meson MX SDIO/MMC controller

This enables the new Amlogic Meson MX SDIO/MMC controller driver, which
typically connects to the SD card and SDIO wifi module.
The driver is enabled as built-in to allow booting from the SD card.
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm/configs/multi_v7_defconfig

@@ -727,6 +727,7 @@ CONFIG_MMC_OMAP=y
 CONFIG_MMC_OMAP_HS=y
 CONFIG_MMC_ATMELMCI=y
 CONFIG_MMC_SDHCI_MSM=y
+CONFIG_MMC_MESON_MX_SDIO=y
 CONFIG_MMC_MVSDIO=y
 CONFIG_MMC_SDHI=y
 CONFIG_MMC_DW=y