Driver-core: Fix bogus 0 error return in device_add()

If device_add() is called with a device which does not have dev->p set
up, then device_private_init() is called. If that succeeds, then the
error variable is set to 0. Now if the dev_name(dev) check further
down fails, then device_add() correctly terminates, but returns 0.
That of course lets the driver progress. If later another driver uses
this half set up device as parent then device_add() of the child
device explodes and renders sysfs completely unusable.

Set the error to -EINVAL if dev_name() check fails.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: "Hans J. Koch" <hjk@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>