drm/i2c: silence ch7006.h and sil164.h kernel-doc warnings

Mark some members private to silence kernel-doc warnings, and add FIXME
comments.
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/ffc58be256d71e6a98eb9f13337add64458d3476.1709898638.git.jani.nikula@intel.com

include/drm/i2c/ch7006.h

@@ -37,6 +37,7 @@
  * meaning.
  */
 struct ch7006_encoder_params {
+	/* private: FIXME: document the members */
 	enum {
 		CH7006_FORMAT_RGB16 = 0,
 		CH7006_FORMAT_YCrCb24m16,

include/drm/i2c/sil164.h

@@ -36,6 +36,7 @@
  * See "http://www.siliconimage.com/docs/SiI-DS-0021-E-164.pdf".
  */
 struct sil164_encoder_params {
+	/* private: FIXME: document the members */
 	enum {
 		SIL164_INPUT_EDGE_FALLING = 0,
 		SIL164_INPUT_EDGE_RISING