There is no locking in init_uio_class so multiple
drivers can race and create multiple uio classes.
Fix this by simplifying the code. In particular always
register the uio class during module_init and make things
simpler.
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Hans J. Koch <hjk@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>