spi: spi-qcom-qspi: Set an autosuspend delay of 250 ms

In commit cff80645d6 ("spi: spi-qcom-qspi: Add interconnect support")
the spi_geni_runtime_suspend() and spi_geni_runtime_resume()
became a bit slower.  Measuring on my hardware I see numbers in the
hundreds of microseconds now.

Let's use autosuspend to help avoid some of the overhead.  Now if
we're doing a bunch of transfers we won't need to be constantly
chruning.

The number 250 ms for the autosuspend delay was picked a bit
arbitrarily, so if someone has measurements showing a better value we
could easily change this.

Fixes: cff80645d6 ("spi: spi-qcom-qspi: Add interconnect support")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Rajendra Nayak <rnayak@codeaurora.org>
Tested-by: Rajendra Nayak <rnayak@codeaurora.org>
Reviewed-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>
Reviewed-by: Akash Asthana <akashast@codeaurora.org>
Link: https://lore.kernel.org/r/20200709075113.v2.2.I3c56d655737c89bd9b766567a04b0854db1a4152@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/spi/spi-qcom-qspi.c

@@ -553,6 +553,8 @@ static int qcom_qspi_probe(struct platform_device *pdev)
 		goto exit_probe_master_put;
 	}
 
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_set_autosuspend_delay(dev, 250);
 	pm_runtime_enable(dev);
 
 	ret = spi_register_master(master);