Remove av1_cost_bit()

It's more efficient to use av1_cost_literal() instead.

Change-Id: I50727d4a4ee06492b373c2e7831c224c5eae8735

av1/encoder/rdopt.c

diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 62911d0..d6edcf5 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -363,9 +363,9 @@
   const int m = (1 << l) - n;
   if (l == 0) return 0;
   if (v < m)
-    return (l - 1) * av1_cost_bit(128, 0);
+    return av1_cost_literal(l - 1);
   else
-    return l * av1_cost_bit(128, 0);
+    return av1_cost_literal(l);
 }
 
 // constants for prune 1 and prune 2 decision boundaries