HID: rename hid-drff.c to hid-dr.c

Rename drivers/hid/hid-drff.c (a DragonRise Inc. force feedback gamepad driver)
to driver/hid/hid-dr.c.

This prepares it for addition of support for another gamepad, without force
feedback.

Signed-off-by: Nikolai Kondrashov <spbnick@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>