ftrace: Simplify the hash calculation

No need to add a check to subtract the number of bits if bits is zero after
fls(). Just divide the size by two before calling it. This does give the
same answer for size of 0 and 1, but that's fine.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -1368,11 +1368,10 @@ static struct ftrace_hash *dup_hash(struct ftrace_hash *src, int size)
 	int i;
 
 	/*
-	 * Make the hash size about 1/2 the # found
+	 * Use around half the size (max bit of it), but
+	 * a minimum of 2 is fine (as size of 0 or 1 both give 1 for bits).
 	 */
-	bits = fls(size);
-	if (bits)
-		bits--;
+	bits = fls(size / 2);
 
 	/* Don't allocate too much */
 	if (bits > FTRACE_HASH_MAX_BITS)