mmc: pci: Add CONFIG_MMC_PCI

We don't want pci_mmc to compile every time x86 compiles, only when
there's a platform that needs it. For that reason, we're adding a new
CONFIG_MMC_PCI which platforms can choose to enable.

Suggested-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
diff --git a/drivers/mmc/Kconfig b/drivers/mmc/Kconfig
index ddef59a..78091cc 100644
--- a/drivers/mmc/Kconfig
+++ b/drivers/mmc/Kconfig
@@ -122,6 +122,14 @@
 
 	  If unsure, say N.
 
+config MMC_PCI
+	bool "Support for MMC controllers on PCI"
+	help
+	  This selects PCI-based MMC controllers.
+	  If you have an MMC controller on a PCI bus, say Y here.
+
+	  If unsure, say N.
+
 config MMC_OMAP_HS
 	bool "TI OMAP High Speed Multimedia Card Interface support"
 	help