i2c: enable async suspend/resume on i2c client devices

This enables the async suspend for i2c client devices. This reduces
the suspend/resume time considerably on platforms where i2c devices
can take a lot of time (hundreds of ms) to resume.

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