uio: pruss: fix error handling in probe

There are two bugs here.  First the error codes weren't set on several
paths.  And second, if the call to request_threaded_irq() inside
uio_register_device() fails then it would lead to a double free when
we call uio_unregister_device() inside pruss_cleanup().

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>