Kobject: change drivers/firmware/efivars.c to use kobject_init_and_add

Stop using kobject_register, as this way we can control the sending of
the uevent properly, after everything is properly initialized.

Cc: Matt Domsch <Matt_Domsch@dell.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>