fstab: bring in line with CWM partition naming guidelines

- internal SD is /sdcard
- external SD is /external_sd
- enables selecting internal/external SD when performing
backup, restore, install

Author: C3C0

recovery/recovery.fstab

@@ -2,7 +2,7 @@
 /system         ext4        /dev/block/mmcblk0p5
 /cache          ext4        /dev/block/mmcblk0p6
 /data           ext4        /dev/block/mmcblk0p7
-/storage        vfat        /dev/block/mmcblk0p8
-/sdcard         vfat        /dev/block/mmcblk1p1
+/sdcard         vfat        /dev/block/mmcblk0p8
+/external_sd    vfat        /dev/block/mmcblk1p1
 /boot           emmc        /dev/bootimg
 /recovery       emmc        /dev/recovery