leds: as3668: Driver for the ams Osram 4-channel i2c LED driver

leds: as3668: Driver for the ams Osram 4-channel i2c LED driver

Since there were no existing drivers for the AS3668 or related devices,
a new driver was introduced in a separate file. Similar devices were
reviewed, but none shared enough characteristics to justify code reuse.
As a result, this driver is written specifically for the AS3668.

Signed-off-by: Lukas Timmermann <linux@timmermann.space>
Link: https://patch.msgid.link/20260118165010.902086-3-linux@timmermann.space
Signed-off-by: Lee Jones <lee@kernel.org>