usb: implement attach kernel driver feature

FreeBSD's USB framework supports detaching kernel drivers to allow
user space applications to exclusively claim USB interfaces. However,
it lacked support for reattaching the kernel driver afterward.

This commit adds the missing functionality, enabling user space
to return control of the device back to the kernel.

Reviewed by: lwhsu
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D52122