TF300T: Changes to fstab.cardhu for mounting. Moving recovery.fstab entries to fstab.cardhu.
Modyfied BoardConfig.mk to include the fstab.cardhu for recovery mounting.
Removed recovery.fstab because it is not needed any more.
Patched common.py and tf300t_ota_from_target_files with the changes from the tf700t device config.
Added mount dir in recovery/init.rc for external_sd
Change-Id: I7e1b3bb665a601f769cb39446075dcf02eec21f5