drm/msm/hdmi: simplify extp clock handling

With the extp being the only "power" clock left, remove the surrounding
loops and handle the extp clock directly.

Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/651710/
Link: https://lore.kernel.org/r/20250505-fd-hdmi-hpd-v5-4-48541f76318c@oss.qualcomm.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>