HID: Add support for Conceptronic CLLRCMCE

There is only one extra button for Conceptronic that wasn't yet present.
The button has code 0xffbc0027 and the description is "Toggle between
display ratios". So I picked KEY_MODE for this button.

Signed-off-by: Kees Bakker <kees.bakker@xs4all.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>