drivers: led: ht16k33: add LED driver for Holtek HT16K33 LED driver

The HT16K33 is a memory mapping, multifunction LED controller
driver. The controller supports up to 128 LEDs (up to 16 rows and 8
commons) and matrix key scan circuit of up to 13x3 keys.

This commit add support for the LED driver functionality of the
HT16K33.

Signed-off-by: Henrik Brix Andersen <henrik@brixandersen.dk>