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/rpi_3_defconfig b/configs/rpi_3_defconfig
index 1618bee..a4c7f69 100644
--- a/configs/rpi_3_defconfig
+++ b/configs/rpi_3_defconfig
@@ -15,6 +15,7 @@
 # CONFIG_CMD_FPGA is not set
 CONFIG_CMD_GPIO=y
 CONFIG_OF_EMBED=y
+CONFIG_MMC_SDHCI=y
 # CONFIG_REQUIRE_SERIAL_CONSOLE is not set
 CONFIG_USB=y
 CONFIG_USB_STORAGE=y