driver core: Skip unnecessary work when device doesn't have sync_state()

A bunch of busy work is done for devices that don't have sync_state()
support. Stop doing the busy work.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200221080510.197337-4-saravanak@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>