arm64: configs: enable SDHCI driver for Xenon

This patch enables the driver for the SDHCI controller found on the
Marvell Armada 3700 and 7K/8K ARM64 SoCs.
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm64/configs/defconfig

@@ -401,6 +401,7 @@ CONFIG_MMC_DW_EXYNOS=y
 CONFIG_MMC_DW_K3=y
 CONFIG_MMC_DW_ROCKCHIP=y
 CONFIG_MMC_SUNXI=y
+CONFIG_MMC_SDHCI_XENON=y
 CONFIG_NEW_LEDS=y
 CONFIG_LEDS_CLASS=y
 CONFIG_LEDS_GPIO=y