lib/sort.c optimization

Hello, I fixed and tested a small bug in lib/sort.c file, heap sort
function.

The fix avoids unnecessary swap of contents when i is 0 (saves few loads
and stores), which happens every time sort function is called.  I felt the
fix is worth bringing it to your attention given the importance and
frequent use of the sort function.
Acked-by: NMatt Mackall <mpm@selenic.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

lib/sort.c

@@ -67,7 +67,7 @@ void sort(void *base, size_t num, size_t size,
 	}
 
 	/* sort */
-	for (i = n - size; i >= 0; i -= size) {
+	for (i = n - size; i > 0; i -= size) {
 		swap(base, base + i, size);
 		for (r = 0; r * 2 + size < i; r = c) {
 			c = r * 2 + size;