usb: xhci: plat: Enable async suspend/resume

USB host controllers can take a significant amount of time to suspend
and resume, adding several hundred miliseconds to the kernel resume
time. Since the XHCI controller has no outside dependencies (other than
clocks, which are suspended late/resumed early), allow it to suspend and
resume asynchronously.
Signed-off-by: NAndrew Bresticker <abrestic@chromium.org>
Tested-by: NAndrew Bresticker <abrestic@chromium.org>
Tested-by: NRobert Foss <robert.foss@collabora.com>
Signed-off-by: NRobert Foss <robert.foss@collabora.com>
Reviewed-by: NBaolin Wang <baolin.wang@linaro.org>
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-plat.c

@@ -277,6 +277,8 @@ static int xhci_plat_probe(struct platform_device *pdev)
 	if (ret)
 		goto dealloc_usb2_hcd;
 
+	device_enable_async_suspend(&pdev->dev);
+
 	return 0;