USB: serial: mos7720: fix parport use-after-free on probe errors

USB: serial: mos7720: fix parport use-after-free on probe errors

BugLink: http://bugs.launchpad.net/bugs/1655969
commit 75dd211e773afcbc264677b0749d1cf7d937ab2d upstream.

Do not submit the interrupt URB until after the parport has been
successfully registered to avoid another use-after-free in the
completion handler when accessing the freed parport private data in case
of a racing completion.

Fixes: b69578df7e98 ("USB: usbserial: mos7720: add support for parallel port on moschip 7715")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>