i2c: rk3x: Make sure the i2c transfer to be finished before system reboot

i2c: rk3x: Make sure the i2c transfer to be finished before system reboot

If the system rebooted, there might be i2c transfer at the
same time, it will make something unpredictable, because
the i2c host was reseted, but the slave device wasn't, such
as rk808 pmic, so make sure the i2c transfer to be finished
before system shutdown at the reset mode.

Change-Id: I3c09f3acbe86595c295edc191aa38351adb7d5dc
Signed-off-by: David Wu <david.wu@rock-chips.com>
Signed-off-by: Jianqun Xu <jay.xu@rock-chips.com>