dt-bindings: leds: spmi-flash-led: Add pm6150l compatible

Add the compatible for the flash-led block found on pm6150l PMIC.

Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20221209-fp4-pm6150l-flash-v1-1-531521eb2a72@fairphone.com