HID: playstation: make LED brightness adjustable in ps_led_register.

Make the max_brightness adjustable through ps_led_info struct. This
paves the way for a next DualShock4 patch to allow larger brightness
values.

Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>