USB: serial: ark3116: fix open error handling

commit b631433b175f1002a31020e09bbfc2e5caecf290 upstream.

Fix open error handling which failed to detect errors when reading the
MSR and LSR registers, something which could lead to the shadow
registers being initialised from errnos.

Note that calling the generic close implementation is sufficient in the
error paths as the interrupt urb has not yet been submitted and the
register updates have not been made.

Fixes: f4c1e8d597d1 ("USB: ark3116: Make existing functions 16450-aware
and add close and release functions.")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>