The mp3309 has two configuration registers, named according to their
address (0x00 and 0x01).
In the second register (0x01), the bit DIMS (Dimming Mode Select) must
be always 0 (zero), in both analog (via I2C commands) and PWM dimming
mode.

In the initial driver version, the DIMS bit was set in PWM mode and
reset in analog mode.
But if the DIMS bit is set in pwm dimming mode and other devices are
connected on the same I2C bus, every I2C commands on the bus generates a
flickering on the LEDs powered by the mp3309c.

This change concerns the chip initialization and does not impact any
existing device-tree configuration.
Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240417153105.1794134-2-f.suligoi@asem.itSigned-off-by: Lee Jones <lee@kernel.org>