drm/msm/hdmi: make 'msm_hdmi_pm_ops' static

drm/msm/hdmi: make 'msm_hdmi_pm_ops' static

The struct 'msm_hdmi_pm_ops' is not used outside of the
file it is defined in, so make it static.

Fixes the following sparse warning:
drivers/gpu/drm/msm/hdmi/hdmi.c:432:1: warning: symbol 'msm_hdmi_pm_ops' was not declared. Should it be static?

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/710583/
Link: https://lore.kernel.org/r/20260310132501.195954-1-ben.dooks@codethink.co.uk
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>