usb: check for companion controller in uclass

usb: check for companion controller in uclass

EHCI is usually used with companion controller (like OHCI) as companion
controller. This information on the companion is missing currently in
companion drivers.
So, if the usb-uclass isn't aware, it may scan busses in any order: OHCI
first, then EHCI.
This is seen on STM32MP1 where DT probing makes the probe order to occur
by increasing address (OHCI address < EHCI address).

When a low speed or full-speed device is plugged in, it's not detected as
EHCI should first detect it, and give ownership (handover) to OHCI.

Current situation on STM32MP1 (with a low speed device plugged-in)
STM32MP> usb start
starting USB...
Bus usb@5800c000: USB OHCI 1.0
Bus usb@5800d000: USB EHCI 1.00
scanning bus usb@5800c000 for devices... 1 USB Device(s) found
scanning bus usb@5800d000 for devices... 1 USB Device(s) found
   scanning usb for storage devices... 0 Storage Device(s) found

The "companion" property in the device tree allow to retrieve companion
controller information, from the EHCI node. This allow marking the
companion driver as such.

With this patch (same low speed device plugged in):
STM32MP> usb start
starting USB...
Bus usb@5800c000: USB OHCI 1.0
Bus usb@5800d000: USB EHCI 1.00
scanning bus usb@5800d000 for devices... 1 USB Device(s) found
scanning bus usb@5800c000 for devices... 2 USB Device(s) found
   scanning usb for storage devices... 0 Storage Device(s) found
STM32MP> usb tree
USB device tree:
1  Hub (12 Mb/s, 0mA)
|   U-Boot Root Hub
|
+-2  Human Interface (1.5 Mb/s, 100mA)
   HP HP USB 1000dpi Laser Mouse

1  Hub (480 Mb/s, 0mA)
 u-boot EHCI Host Controller

This also optimize bus scan when a High speed device is plugged in, as
the usb-uclass skips OHCI in this case:

STM32MP> usb reset
resetting USB...
Bus usb@5800c000: USB OHCI 1.0
Bus usb@5800d000: USB EHCI 1.00
scanning bus usb@5800d000 for devices... 2 USB Device(s) found
   scanning usb for storage devices... 1 Storage Device(s) found
STM32MP> usb tree
USB device tree:
1  Hub (480 Mb/s, 0mA)
|  u-boot EHCI Host Controller
|
+-2  Mass Storage (480 Mb/s, 200mA)
   SanDisk Cruzer Blade 03003432021922011407

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Reviewed-by: Marek Vasut <marex@denx.de>