FPMT: Fix the computation of num_mod_workers for parallel frames

The computation of num_mod_workers[] for each of the parallel frames is
corrected to account for the uneven number of workers per frame when the
total workers is a non-multiple of the number of parallel frames.

Change-Id: Iad65e4933506b008912316e309151f697bbe274c

av1/encoder/ethread.c

diff --git a/av1/encoder/ethread.c b/av1/encoder/ethread.c
index 9e81d7a..5fcc7e4 100644
--- a/av1/encoder/ethread.c
+++ b/av1/encoder/ethread.c
@@ -840,7 +840,7 @@
     mt_info->num_workers = AOMMIN(workers_per_frame, num_workers - i);
     for (int j = MOD_FP; j < NUM_MT_MODULES; j++) {
       mt_info->num_mod_workers[j] =
-          AOMMIN(workers_per_frame, ppi->p_mt_info.num_mod_workers[j]);
+          AOMMIN(mt_info->num_workers, ppi->p_mt_info.num_mod_workers[j]);
     }
 
     frame_worker->hook = hook;