USB: serial: io_edgeport: fix memory leaks in probe error path

[ Upstream commit c8d62957d450cc1a22ce3242908709fe367ddc8e ]

URBs and buffers allocated in attach for Epic devices would never be
deallocated in case of a later probe error (e.g. failure to allocate
minor numbers) as disconnect is then never called.

Fix by moving deallocation to release and making sure that the
URBs are first unlinked.

Fixes: f9c99bb8 ("USB: usb-serial: replace shutdown with disconnect,
release")
Cc: stable <stable@vger.kernel.org>	# v2.6.31
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>