hidapi: do not enumerate XInput devices owned by a kernel driver via libusb on macOS

[tmkk]

• I confirm that I am the author of this code and release it to the SDL project under the Zlib license. This contribution does not contain code from other sources, including code generated by a Large Language Model ("AI").

Description

With commit 18fc4d9 now XInput devices on macOS are enumerated by libusb in hidapi. Since devices enumerated by libusb are not enumerated by the platform backend:

SDL/src/hidapi/SDL_hidapi.c

Lines 1440 to 1445 in da8aa39

	for (dev = usb_devs; dev; dev = dev->next) {
	AddDeviceToEnumeration("libusb", dev, &devs, &last);
	#ifdef HAVE_PLATFORM_BACKEND
	RemoveDeviceFromEnumeration("raw", dev, &raw_devs, PLATFORM_hid_free_enumeration);
	#endif
	}

When a device is enumerated by libusb but it cannot be opened (usually due to libusb_claim_interface failure), it doesn't fallback to the platform backend. This is ok for GCController devices but it is a problem for devices which work with the hidapi platform backend. XInput controllers working with 360Controller driver are examples.

This PR adds checking if a device is already owned by KEXT by libusb_kernel_driver_active function when enumerating devices.

[slouken]

Merged, thanks!