generic: backport support for KTD2026/7 rgb(w) led controller

generic: backport support for KTD2026/7 rgb(w) led controller

This commit adds the Linux kernel mainline driver "leds-ktd202x" for the
KinetIC KTD2026 and KTD2027 RGB/RBGW controller with I2C interface that was
introduced in kernel version 6.7, last changed in mainline on 2024-05-31.

At least the Acer Connect Vero W6m (a variant of the Acer Predator Connect
W6 without 2.5G eth1 port, usb3 port, and the 6 on-board gpio RGB LEDs) is
equipped with a KTD2026 (and a single RGB LED attached to it used by the
stock firmware as status LED), and maybe other router devices also are.

Signed-off-by: George Oldfort <openwrt@10099.de>
Link: https://github.com/openwrt/openwrt/pull/16860
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>