Fix memory leaks when failing to create a uinput device

Fix memory leaks when failing to create a uinput device

For an invalid fd, or a failure to open the device, the pre-allocated uinput
device struct would leak.

We can drop the open_uinput() function now, since skipping to the error
handling means we'll return -errno anyway.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>