generic swap(): ext4: remove local swap() macro

Use the new generic implementation.
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/ext4/namei.c

@@ -74,10 +74,6 @@ static struct buffer_head *ext4_append(handle_t *handle,
 #define assert(test) J_ASSERT(test)
 #endif
 
-#ifndef swap
-#define swap(x, y) do { typeof(x) z = x; x = y; y = z; } while (0)
-#endif
-
 #ifdef DX_DEBUG
 #define dxtrace(command) command
 #else