backlight: as3711_bl: Handle deferred probe

Don't pollute dmesg on deferred probe and simplify the code with
dev_err_probe().

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240305-backlight-probe-v2-4-609b0cf24bde@linaro.org


Signed-off-by: Lee Jones <lee@kernel.org>