leds: lp5523: remove unnecessary writing commands

This patch reduces the number of programming commands.

(Count of sending commands)
Old code: 32 + program size (32 counts for clearing program memory)
New code: 32

Pattern buffer is initialized to 0 in this function.
Just update new program data and remaining buffers are filled with 0.
So it's needless to clear whole area.

Signed-off-by: Milo Kim <milo.kim@ti.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>