mmc: replace CONFIG_GENERIC_MMC with CONFIG_MMC

Now CONFIG_GENERIC_MMC and CONFIG_MMC match for all defconfig.
We do not need two options for the same feature.  Deprecate the
former.

This commit was generated with the sed script 's/GENERIC_MMC/MMC/'
and manual fixup of drivers/mmc/Kconfig.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b2d6e80..a17ba2c 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -654,7 +654,7 @@
 	imply SPL_LIBCOMMON_SUPPORT
 	imply SPL_LIBDISK_SUPPORT
 	imply SPL_LIBGENERIC_SUPPORT
-	imply SPL_MMC_SUPPORT if GENERIC_MMC
+	imply SPL_MMC_SUPPORT if MMC
 	imply SPL_POWER_SUPPORT
 	imply SPL_SERIAL_SUPPORT