Fix naming of av1_tpl_stats_init_txfm_stats()

BUG=aomedia:3011

Change-Id: Iaece286da3241a0f8c02bbd1a251bd4f943b2ad0

av1/encoder/tpl_model.h

diff --git a/av1/encoder/tpl_model.h b/av1/encoder/tpl_model.h
index 592e285..1937f3e 100644
--- a/av1/encoder/tpl_model.h
+++ b/av1/encoder/tpl_model.h
@@ -309,10 +309,10 @@
  *\ingroup tpl_modelling
  *
  * \param[in]    tpl_frame       pointer of tpl frame data structure
- * \param[in]    coeff_num       number of coefficients per transform block
+ * \param[in]    tpl_bsize_1d    length of the side of a square transform block
  *
  */
-void av1_tpl_stats_init_txfm_stats(TplDepFrame *tpl_frame, int coeff_num);
+void av1_tpl_stats_init_txfm_stats(TplDepFrame *tpl_frame, int tpl_bsize_1d);
 
 /*!\brief  Estimate coefficient entropy using Laplace dsitribution
  *