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/board/samsung/common/board.c b/board/samsung/common/board.c
index 49e4db2..1762696 100644
--- a/board/samsung/common/board.c
+++ b/board/samsung/common/board.c
@@ -250,7 +250,7 @@
 	return 0;
 }
 
-#ifdef CONFIG_GENERIC_MMC
+#ifdef CONFIG_MMC
 static int init_mmc(void)
 {
 #ifdef CONFIG_MMC_SDHCI