HID: add omitted hid-zydacron.c file

Commit a9885c8f

 ("HID: Zydacron Remote Control driver") added
hid-zydracon driver by Don Prince, but mistakenly omitted hid-zydracon.c
file itself. Properly add the file.

Reported-by: Don Prince <dhprince.devel@yahoo.co.uk>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>