add cifs example, disable busybox internal cifs code

package/base-files/src/etc/fstab

@@ -6,3 +6,5 @@ devpts          /dev/pts       devpts   defaults,gid=5,mode=620   0      0
 tmpfs           /dev/shm       tmpfs    mode=0777         0      0
 tmpfs           /tmp           tmpfs    mode=1777         0      0
 sysfs           /sys           sysfs    defaults          0      0
+# example for cifs
+#//192.168.1.1/music     /music/test        cifs    ro,password=linux123,username=adk,iocharset=utf8,sec=ntlm     0       0

package/busybox/config/util-linux/Config.in

@@ -572,7 +572,7 @@ config BUSYBOX_FEATURE_MOUNT_NFS
 
 config BUSYBOX_FEATURE_MOUNT_CIFS
 	bool "Support mounting CIFS/SMB file systems"
-	default y
+	default n
 	depends on BUSYBOX_MOUNT
 	help
 	  Enable support for samba mounts.