ARM: dts: qcom: apq8026-samsung-matisse-wifi: Add display backlight

Uses ti,lp8556 backlight with clk-pwm.

Signed-off-by: Matti Lehtimäki <matti.lehtimaki@gmail.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230111183502.706151-1-matti.lehtimaki@gmail.com