drivers: serial: jsm: fix some leaks in probe

This error path needs to unwind instead of just returning directly.

Fixes: 03a8482c

 ("drivers: serial: jsm: Enable support for Digi Classic adapters")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YyxFh1+lOeZ9WfKO@kili


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>