arm64: dts: qcom: sdm845-shift-axolotl: enable flash LEDs

The SHIFT6mq (axolotl) is an SDM845-based smartphone with 2 flash LEDs.
One LED is white, the other one is yellow. Define both LEDs in the DTS
so they can be used as flash or torch and enable the flash LED
controller to control them in PMI8998.

Signed-off-by: Dylan Van Assche <me@dylanvanassche.be>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230518133113.273880-4-me@dylanvanassche.be