component: ignore multiple additions of the same component
Permit masters to call component_master_add_child() and match the same
child multiple times. This may happen if there's multiple connections
to a single component device from other devices. In such scenarios,
we should not return a failure, but instead ignore the attempt.
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>