i2c-puv3: Use struct dev_pm_ops for power management

Make the PKUnity-v3 SoC I2C controller driver define its suspend
callback through a struct dev_pm_ops object rather than by using
a legacy PM hook in struct platform_driver.  The empty resume
callback is not necessary, so remove it.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>