i2c: designware: Enable async suspend / resume of designware devices

Mark the designware devices for asynchronous suspend. With this, the
resume for designware devices does not get stuck behind other unrelated
devices (e.g. intel_backlight that takes hundreds of ms to resume,
waiting for its parent devices).

Signed-off-by: Rajat Jain <rajatja@google.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>