mvebu: make MMC driver for Clearfog builtin

microSD is the primary boot media for the Clearfog Pro board, and should
work unconditionally.

Signed-off-by: Josua Mayer <josua.mayer97@gmail.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name> [cleanup]

target/linux/mvebu/config-4.4

@@ -246,7 +246,12 @@ CONFIG_MEMORY=y
 CONFIG_MIGHT_HAVE_CACHE_L2X0=y
 CONFIG_MIGHT_HAVE_PCI=y
 CONFIG_MMC=y
+CONFIG_MMC_BLOCK=y
 CONFIG_MMC_MVSDIO=y
+CONFIG_MMC_SDHCI=y
+# CONFIG_MMC_SDHCI_PCI is not set
+CONFIG_MMC_SDHCI_PLTFM=y
+CONFIG_MMC_SDHCI_PXAV3=y
 # CONFIG_MMC_TIFM_SD is not set
 CONFIG_MODULES_USE_ELF_REL=y
 CONFIG_MTD_CFI_STAA=y