arm64: dts: qcom: msm8916-samsung-grandmax: Add properties function and color for keyled

keyled is white, and used as touchkey LEDs.
Add properties function and color for keyled.

Signed-off-by: Lin, Meng-Bo <linmengbo0689@protonmail.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221117144717.17886-1-linmengbo0689@protonmail.com