pxa: move mmc drivers to drivers/mmc

introduce new macro CONFIG_PXA_MMC to activate it

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/include/configs/pleb2.h b/include/configs/pleb2.h
index 23398e3..59741a9 100644
--- a/include/configs/pleb2.h
+++ b/include/configs/pleb2.h
@@ -132,6 +132,11 @@
 						/* valid baudrates */
 #define CONFIG_SYS_BAUDRATE_TABLE	{ 9600, 19200, 38400, 57600, 115200 }
 
+#ifdef CONFIG_MMC
+#define CONFIG_PXA_MMC
+#define CONFIG_CMD_MMC
+#endif
+
 /*
  * Stack sizes
  *