i2c: Remove support for legacy PM

There haven't been any I2C driver that use the legacy suspend/resume
callbacks for a while now and new drivers are supposed to use PM ops. So
remove support for legacy suspend/resume for I2C drivers.

Since there aren't any special bus specific things to do during
suspend/resume and since the PM core will automatically fallback directly to
using the device's PM ops if no bus PM ops are specified there is no need to
have any I2C bus PM ops.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>