kobject: return the result of uevent sending by netlink

We need to return the result of uevent sending by netlink
to caller, when uevent_helper is disabled and CONFIG_NET
is defined.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>