delogo: Fix function description

The algorithm works on src and writes to dst, not the other way
around.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/vf_delogo.c

@@ -35,8 +35,8 @@
 #include "video.h"
 
 /**
- * Apply a simple delogo algorithm to the image in dst and put the
- * result in src.
+ * Apply a simple delogo algorithm to the image in src and put the
+ * result in dst.
  *
  * The algorithm is only applied to the region specified by the logo
  * parameters.