The unit of buffer size is bits, not bits/s

The corresponding text in the AV1 spec is the following on page 644:

  These requirements depend on the following level, tier, and profile
  dependent variables:
    * ...
    * MaxBufferSize is equal to MaxBitrate multiplied by 1 second

Change-Id: I792d3ffdafe482426c5ade3d80810263baf07e12

av1/decoder/obu.c

diff --git a/av1/decoder/obu.c b/av1/decoder/obu.c
index 815d805..45a3f15 100644
--- a/av1/decoder/obu.c
+++ b/av1/decoder/obu.c
@@ -183,7 +183,7 @@
           aom_internal_error(&pbi->error, AOM_CODEC_UNSUP_BITSTREAM,
                              "AV1 does not support this combination of "
                              "profile, level, and tier.");
-        // Buffer size in bits/s is bitrate in bits/s * 1 s
+        // Buffer size in bits is bitrate in bits/s * 1 s
         seq_params->op_params[i].buffer_size = seq_params->op_params[i].bitrate;
       }
       if (seq_params->timing_info_present &&

av1/encoder/encoder.c

diff --git a/av1/encoder/encoder.c b/av1/encoder/encoder.c
index e32bd64..67b780b 100644
--- a/av1/encoder/encoder.c
+++ b/av1/encoder/encoder.c
@@ -553,7 +553,7 @@
       aom_internal_error(
           &ppi->error, AOM_CODEC_UNSUP_BITSTREAM,
           "AV1 does not support this combination of profile, level, and tier.");
-    // Buffer size in bits/s is bitrate in bits/s * 1 s
+    // Buffer size in bits is bitrate in bits/s * 1 s
     seq_params->op_params[i].buffer_size = seq_params->op_params[i].bitrate;
   }
 }