The xhci driver currently only does the necessary initialization for
endpoints found in the first interface descriptor. Apple USB keyboards
(released 2021) use the second interface descriptor for the HID keyboard
boot protocol. To allow USB drivers to use endpoints from other
interface descriptors the xhci driver needs to ensure these endpoints
are initialized as well.
Use USB_MAX_ACTIVE_INTERFACES to control how many interface descriptors
are considered during endpoint initialisation.
For now define it to 2 as that is sufficient for supporting the Apple
keyboards.

Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Janne Grunau <j@jannau.net>