drm/msm/dp: remove the repeated declaration

Function 'dp_catalog_audio_enable' is declared twice, remove the
repeated declaration.

Cc: Rob Clark <robdclark@gmail.com>
Cc: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Link: https://lore.kernel.org/r/1621945327-10871-1-git-send-email-zhangshaokun@hisilicon.com
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>