Input: serio - drop warnings in case of EPROBE_DEFER from serio_find_driver()

Now serio_find_driver() will print warnings in case device_attach()
returns -EPROBE_DEFER. Those warnings are obsolete, in genral, because:
- DD core can report the same if required
- since commit 013c074f ("PM / sleep: prohibit devices probing
during suspend/hibernation") the devices probing is prohibited during
System suspend and deferred device will be carefully reprobed once
Resume is finished.

Hence, drop warnings in case of EPROBE_DEFER from serio_find_driver().

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>