usb: Probe EHCI, OHCI controllers asynchronously

initcall_debug shows that OHCI controllers take ~60ms to probe on
Rockchip RK3399 systems:

  probe of fe3a0000.usb returned 1 after 58941 usecs

A few of these can add up to waste non-trivial amounts of time at boot.

These host controllers don't provide resources to other drivers, so
this shouldn't contribute to exposing race conditions.

Chrome OS kernels have carried this patch on some systems for a while
without issues. Similar patches have been merged for a variety of (e)MMC
host controllers for similar reasons.

[Brian: rewrote commit message, refreshed, but retained dtor's original
 authorship ]
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NDmitry Torokhov <dtor@chromium.org>
Signed-off-by: NBrian Norris <briannorris@chromium.org>
Link: https://lore.kernel.org/r/20220518150150.1.Ie8ea0e945a9c15066237014be219eed60066d493@changeidSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-platform.c

@@ -518,6 +518,7 @@ static struct platform_driver ehci_platform_driver = {
 		.pm	= pm_ptr(&ehci_platform_pm_ops),
 		.of_match_table = vt8500_ehci_ids,
 		.acpi_match_table = ACPI_PTR(ehci_acpi_match),
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 	}
 };
 

drivers/usb/host/ohci-platform.c

@@ -334,6 +334,7 @@ static struct platform_driver ohci_platform_driver = {
 		.name	= "ohci-platform",
 		.pm	= &ohci_platform_pm_ops,
 		.of_match_table = ohci_platform_ids,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 	}
 };