i2c: enable async suspend/resume for i2c adapters

Enable async suspend/resume of i2c adapters. It enormously helps with
reducing the resume time of systems (as much as 20%-40%) where I2C devices
can take significant time (100s of ms) to resume.
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>

drivers/i2c/i2c-core-base.c

@@ -1577,6 +1577,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
 	if (res)
 		goto out_reg;
 
+	device_enable_async_suspend(&adap->dev);
 	pm_runtime_no_callbacks(&adap->dev);
 	pm_suspend_ignore_children(&adap->dev, true);
 	pm_runtime_enable(&adap->dev);