pixelutils: indent comments in pixdesc.h to be clearer

Signed-off-by: Peter Cordes <peter@cordes.ca>

libavutil/pixdesc.h

@@ -93,9 +93,9 @@ typedef struct AVPixFmtDescriptor {
      * Parameters that describe how pixels are packed.
      * If the format has 2 or 4 components, then alpha is last.
      * If the format has 1 or 2 components, then luma is 0.
-     * If the format has 3 or 4 components,
-     * if the RGB flag is set then 0 is red, 1 is green and 2 is blue;
-     * otherwise 0 is luma, 1 is chroma-U and 2 is chroma-V.
+     * If the format has 3 or 4 components:
+     *   if the RGB flag is set then 0 is red, 1 is green and 2 is blue;
+     *   otherwise 0 is luma, 1 is chroma-U and 2 is chroma-V.
      */
     AVComponentDescriptor comp[4];