drm/msm/hdmi: get rid of hdmi_mode

Use connector->display_info.is_hdmi instead of manually using
drm_detect_hdmi_monitor().

Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/639657/
Link: https://lore.kernel.org/r/20250226-bridge-hdmi-connector-v8-4-340af24b35cc@linaro.org