HID: Create a common generic driver

Move the hid drivers of the bus drivers to a common generic hid
driver, and make it a proper module. This ought to simplify device
handling moving forward.

Cc: Gustavo Padovan <gustavo@padovan.org>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>