HID: hyperv: Implement a stub raw_request() entry point

commit 3c86726c

 ("HID: make .raw_request mandatory") made .raw_request
mandatory and broke the Hyper-V mouse driver. This patch fixes the problem.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>