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/common/board_r.c b/common/board_r.c
index d69a33c..9f34b85 100644
--- a/common/board_r.c
+++ b/common/board_r.c
@@ -432,7 +432,7 @@
 }
 #endif
 
-#ifdef CONFIG_GENERIC_MMC
+#ifdef CONFIG_MMC
 static int initr_mmc(void)
 {
 	puts("MMC:   ");
@@ -815,7 +815,7 @@
 #ifdef CONFIG_CMD_ONENAND
 	initr_onenand,
 #endif
-#ifdef CONFIG_GENERIC_MMC
+#ifdef CONFIG_MMC
 	initr_mmc,
 #endif
 #ifdef CONFIG_HAS_DATAFLASH