spi: qup: skip clk_disable_unprepare if the device is already runtime suspended

If the spi device is already runtime suspended, if spi_qup_suspend is
executed during suspend-to-idle or suspend-to-ram it will result in the
a splat from unpreparing a non-prepared clock.

This patch fixes the issue by executing clk_disable_unprepare conditionally
in spi_qup_suspend.

[Reworded commit message to remove irrelevant backtrace -- broonie]
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>
Tested-by: NAndy Gross <andy.gross@linaro.org>
Signed-off-by: NMark Brown <broonie@kernel.org>

drivers/spi/spi-qup.c

@@ -982,8 +982,10 @@ static int spi_qup_suspend(struct device *device)
 	if (ret)
 		return ret;
 
-	clk_disable_unprepare(controller->cclk);
-	clk_disable_unprepare(controller->iclk);
+	if (!pm_runtime_suspended(device)) {
+		clk_disable_unprepare(controller->cclk);
+		clk_disable_unprepare(controller->iclk);
+	}
 	return 0;
 }