HID: hid-plantronics: Re-resend Update to map button for PTT products

Add a mapping for Push-To-Talk joystick trigger button.

Tested on ChromeBox/ChromeBook with various Plantronics devices.

Signed-off-by: Terry Junge <terry.junge@plantronics.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>