rose: Transmit packets in rose_xmit not rose_rebuild_header

Patterned after the similar code in net/rom this turns out
to be a trivial obviously correct transmformation.

Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-hams@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>