spi: rockchip: Disable Runtime PM when chip select is asserted

The rockchip spi would stop driving pins when runtime suspended, which
might break slave's xfer(for example cros_ec).

Since we have pullups on those pins, we only need to care about this
when the CS asserted.

So let's keep the spi alive when chip select is asserted.

Also use pm_runtime_put instead of pm_runtime_put_sync.

Suggested-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>