ARM: dts: ux500: Fix LED probing

ARM: dts: ux500: Fix LED probing

The Ux500 HREF LEDs have not been probing properly for a
while as this was introduce:

     ret = of_property_read_u32(np, "color", &led_color);
     if (ret)
             return ret;

Since the device tree did not define the new invented color
attribute, probe was failing.

Define color attributes for the LEDs so they work again.

Link: https://lore.kernel.org/r/20210613123356.880933-1-linus.walleij@linaro.org
Fixes: 92a81562e695 ("leds: lp55xx: Add multicolor framework support to lp55xx")
Cc: stable@vger.kernel.org
Cc: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>