drivers: uio: Fix UIO device registration failure

drivers: uio: Fix UIO device registration failure

commit 5ed0505c713805f89473cdc0bbfb5110dfd840cb upstream.

Until recently uio_get_minor() returned 0 for success and
a negative value on failure.  This became non-negative for suceess and
negative for failure.  Restore the original return value spec so that we can
successfully initialize UIO devices with a non-zero minor device
number.

Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>
Cc: "Hans J. Koch" <hjk@hansjkoch.de>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>