doc/filters: add missed framesync part in filter docs

Add missed framesync part in filter docs.

Reviewed-by: Gyan Doshi <ffmpeg@gyani.pro>
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

doc/filters.texi

@@ -12242,6 +12242,8 @@ this value filter algorithm for connecting components is activated.
 By default value is 0.
 @end table
 
+The @code{hysteresis} filter also supports the @ref{framesync} options.
+
 @section idet
 
 Detect video interlacing type.
@@ -13094,6 +13096,8 @@ set output bit depth, only available for @code{lut2} filter. By default is 0,
 which means bit depth is automatically picked from first input format.
 @end table
 
+The @code{lut2} filter also supports the @ref{framesync} options.
+
 Each of them specifies the expression to use for computing the lookup table for
 the corresponding pixel component values.
 
@@ -21337,6 +21341,8 @@ Size of output frames.  Defaults to the same as the first input.
 
 @end table
 
+The @code{program_opencl} filter also supports the @ref{framesync} options.
+
 The program source file must contain a kernel function with the given name,
 which will be run once for each plane of the output.  Each run on a plane
 gets enqueued as a separate 2D global NDRange with one work-item for each