mmc: move CONFIG_SDHCI to Kconfig, renaming to CONFIG_MMC_SDHCI

Move CONFIG_SDHCI to Kconfig and rename it to CONFIG_MMC_SDHCI.
My motivation for the rename is, ultimately, to make all the MMC
options prefixed with MMC_ and SDHCI options with MMC_SDHCI_,
like Linux.

This commit was created as follows:

[1] Rename the config option with the following command:
find . -name .git -prune -o ! -path ./scripts/config_whitelist.txt \
-type f -print | xargs sed -i -e 's/CONFIG_SDHCI/CONFIG_MMC_SDHCI/g'

[2] create the entry for MMC_SDHCI in drivers/mmc/Kconfig

[3] run "tools/moveconfig.py -y MMC_SDHCI"

[4] add "depends on MMC_SDHCI" to existing SDHCI driver entries

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
diff --git a/configs/dfi-bt700-q7x-151_defconfig b/configs/dfi-bt700-q7x-151_defconfig
index efe1fc7..84f0559 100644
--- a/configs/dfi-bt700-q7x-151_defconfig
+++ b/configs/dfi-bt700-q7x-151_defconfig
@@ -42,6 +42,7 @@
 CONFIG_CPU=y
 CONFIG_DM_I2C=y
 CONFIG_NUVOTON_NCT6102D=y
+CONFIG_MMC_SDHCI=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_GIGADEVICE=y
 CONFIG_SPI_FLASH_MACRONIX=y