HID: uhid: Fix sending events with invalid data

This was detected because events with invalid types were arriving
to userspace.

The code before this patch would only work for the first event in the
queue (when uhid->tail is 0).

Change-Id: I1d6d167d6a8970e2d4af629955a5777338b3c8d6
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Reviewed-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>