add external_sd directory to ramdisk for mounting external sdcard in cwmr
This addition allows external sdcard mounting in recovery by providing the necessary mountpoint.

Change-Id: Iad32e531d9d35b370645dcf729bc5a70cbf21167
Merge branch 'cm-10.1' of github.com:CyanogenMod/android_device_samsung_smdk4412-common into CyanogenMod-cm-10.1

Conflicts:
	recovery.rc