driver core: Fix handling of SYNC_STATE_ONLY + STATELESS device links

Commit 21c27f06 ("driver core: Fix SYNC_STATE_ONLY device link
implementation") didn't completely fix STATELESS + SYNC_STATE_ONLY
handling.

What looks like an optimization in that commit is actually a bug that
causes an if condition to always take the else path. This prevents
reordering of devices in the dpm_list when a DL_FLAG_STATELESS device
link is create on top of an existing DL_FLAG_SYNC_STATE_ONLY device
link.

Fixes: 21c27f06

 ("driver core: Fix SYNC_STATE_ONLY device link implementation")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20200520043626.181820-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>