When we can't find a .ko module to satisfy the firmware request, try
harder by looking for a file to read in directly. We compuse this file's
name by appening the imagename to the firmware path (currently
hard-wired at /boot/firmware). Allow this file to be unload when
firmware_put() releases the last reference, but we don't need to do the
indirection and dance we need to do when unloading the .ko that will
unregister the firmware.