arm64: defconfig: enable CONFIG_MMC_SDHCI_CADENCE

Enable the Cadence SD/SDIO/eMMC controller.  This is used on
Socionext UniPhier SoC family.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Olof Johansson <olof@lixom.net>