firstpass.c: remove av1_firstpass_info_past_count()

This function was added in:
d8cfe16d90 Let firstpass_info support past stats
but never used.

Bug: aomedia:3416,aomedia:3069,aomedia:3070
Change-Id: Ie319ee89aebb256191e2cd03d0c38972edec4b03

av1/encoder/firstpass.c

diff --git a/av1/encoder/firstpass.c b/av1/encoder/firstpass.c
index 416ee42..8bbf79d 100644
--- a/av1/encoder/firstpass.c
+++ b/av1/encoder/firstpass.c
@@ -1590,11 +1590,3 @@
   }
   return 0;
 }
-
-int av1_firstpass_info_past_count(const FIRSTPASS_INFO *firstpass_info,
-                                  int offset_from_cur) {
-  if (offset_from_cur >= -firstpass_info->past_stats_count) {
-    return offset_from_cur + firstpass_info->past_stats_count;
-  }
-  return 0;
-}

av1/encoder/firstpass.h

diff --git a/av1/encoder/firstpass.h b/av1/encoder/firstpass.h
index 0832494..bec9ece 100644
--- a/av1/encoder/firstpass.h
+++ b/av1/encoder/firstpass.h
@@ -323,21 +323,6 @@
 int av1_firstpass_info_future_count(const FIRSTPASS_INFO *firstpass_info,
                                     int offset_from_cur);
 
-/*!\brief Count the past stats before the target in firstpass_info
- * Note that the target stats will NOT be counted.
- * The target index is as follows.
- * (cur_index + offset_from_cur) % firstpass_info->stats_buf_size
- *
- * \ingroup rate_control
- * \param[in]  firstpass_info    struct of firstpass_info.
- * \param[in]  offset_from_cur  target stats's index offset
- *                               from cur_index.
- * \return Number of stats in the past before the target stats
- *         excluding itself.
- */
-int av1_firstpass_info_past_count(const FIRSTPASS_INFO *firstpass_info,
-                                  int offset_from_cur);
-
 /*!\cond */
 #define FC_ANIMATION_THRESH 0.15
 enum {