busybox: unbreak tar of uncompressed files

A patch was added to fix compressed tar files, but broke uncompressed
tar files, this fix is from the busybox mailing list

http://lists.busybox.net/pipermail/busybox/2014-January/080389.html



[YOCTO #7645]

Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>