i2c-s3c2410: Use plain pm_runtime_put()

There's no point in using _sync() as we don't really care if the suspend
has completed immediately.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>