Fix spelling error of "dropped"

Change-Id: Id6a6a06184dd450e3587353df5c5743ed6110ab6
diff --git a/av1/encoder/encoder.c b/av1/encoder/encoder.c
index 9dade55..7000e98 100644
--- a/av1/encoder/encoder.c
+++ b/av1/encoder/encoder.c
@@ -3544,7 +3544,7 @@
   aom_usec_timer_mark(&cmptimer);
   cpi->time_compress_data += aom_usec_timer_elapsed(&cmptimer);
 #endif  // CONFIG_INTERNAL_STATS
-  // Note *size = 0 indicates a dropeed frame for which psnr is not calculated
+  // Note *size = 0 indicates a dropped frame for which psnr is not calculated
   if (cpi->b_calculate_psnr && *size > 0) {
     if (cm->show_existing_frame ||
         (!is_stat_generation_stage(cpi) && cm->show_frame)) {