driver core: Fix device_link_flag_is_sync_state_only()

device_link_flag_is_sync_state_only() correctly returns true on the flags
of an existing device link that only implements sync_state() functionality.
However, it incorrectly and confusingly returns false if it's called with
DL_FLAG_SYNC_STATE_ONLY.

This bug doesn't manifest in any of the existing calls to this function,
but fix this confusing behavior to avoid future bugs.

Fixes: 67cad5c6

 ("driver core: fw_devlink: Add DL_FLAG_CYCLE support to device links")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Tested-by: Xu Yang <xu.yang_2@nxp.com>
Link: https://lore.kernel.org/r/20240202095636.868578-2-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>