i2c: mv64xxx: add suspend/resume support

This commit implements suspend/resume support in the mv64xxx I2C
controller driver. There is no need to implement a ->suspend() hook, as
calling mv64xxx_i2c_hw_init() at ->resume() time is enough.

Signed-off-by: Grzegorz Jaszczyk <jaz@semihalf.com>
Reviewed-by: Nadav Haklai <nadavh@marvell.com>
Reviewed-by: Lior Amsalem <alior@marvell.com>
Tested-by: Lior Amsalem <alior@marvell.com>
[Thomas: switch to dev_pm_ops, fix build warning when !PM.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>