HID: core: rewrite the hid-generic automatic unbind

We actually can have the unbind/rebind logic in hid-core.c, leaving
only the match function in hid-generic.

This makes hid-generic simpler and the whole logic simpler too.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>