Add support for setting the blink rate of the LEDs.  The Sixaxis allows control
over each individual LED, but the Dualshock 4 only has one global control for
controlling the hardware blink rate so individual colors will fall back to
software timers.

Setting the brightness cancels the blinking as per the LED class specifications.

The Sixaxis and Dualshock 4 controllers accept delays in decisecond increments
from 0 to 255 (2550 milliseconds).

The value at index 1 of the DualShock 4 USB output report must be 0xFF or the
light bar won't blink.
Signed-off-by: NFrank Praznik <frank.praznik@oh.rr.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>