HID: Add driver for Logitech gaming keyboards (G15, G15 v2)

Add a driver to stop the extra "G" keys from sending F1 - F12 instead
making them send KEY_GKEY# and also make the non-functional M1 - M3 and MR
keys and the non-functional buttons below the LCD panel properly generated
key events.

Note the connect_mask and gkeys_settings_output_report variables may seem
unnecessary since they are always set to the same value, these are there in
preparation of adding support for the G, M and LCD keys on the G510 kbd.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>