ARM: multi_v7_defconfig: Enable CONFIG_MMC_SDHCI_OMAP

Enable CONFIG_MMC_SDHCI_OMAP so that TI's dra7/k2g based SoC's
can use sdhci-omap for eMMC/SD/SDIO controller..

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>