video/hdmi: Dropped static functions from kernel doc

Dropped static functions from kernel documentation.

v2: Dropped the comments altogether for static functions,
as the definitions seems self explanatory.

Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1559567330-25182-4-git-send-email-uma.shankar@intel.com