mmc: Kconfig: downgrade CONFIG_MMC_DEBUG for host drivers only

We have removed all code depending on CONFIG_MMC_DEBUG
from mmc core now. So it's safe to make CONFIG_MMC_DEBUG
just for host drivers only and we expect to kill this option
in the future.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
index 2242633..66b1749 100644
--- a/drivers/mmc/host/Kconfig
+++ b/drivers/mmc/host/Kconfig
@@ -4,6 +4,15 @@
 
 comment "MMC/SD/SDIO Host Controller Drivers"
 
+config MMC_DEBUG
+	bool "MMC host drivers debugginG"
+	depends on MMC != n
+	help
+	  This is an option for use by developers; most people should
+	  say N here. This enables MMC host driver debugging. And further
+	  added host drivers please don't invent their private macro for
+	  debugging.
+
 config MMC_ARMMMCI
 	tristate "ARM AMBA Multimedia Card Interface support"
 	depends on ARM_AMBA