MAINTAINERS: add UHID entry

Add an UHID entry to the MAINTAINERS file.

Change-Id: Iad79e71619ea469a1348b97591cfab37522b5a95
Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>