xtensa: provide __NR_sync_file_range2 instead of __NR_sync_file_range

xtensa actually uses sync_file_range2 implementation, so it should
define __NR_sync_file_range2 as other architectures that use that
function. That fixes userspace interface (that apparently never worked)
and avoids special-casing xtensa in libc implementations.
See the thread ending at
http://lists.busybox.net/pipermail/uclibc/2015-February/048833.html
for more details.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/include/uapi/asm/unistd.h

@@ -715,7 +715,7 @@ __SYSCALL(323, sys_process_vm_writev, 6)
 __SYSCALL(324, sys_name_to_handle_at, 5)
 #define __NR_open_by_handle_at			325
 __SYSCALL(325, sys_open_by_handle_at, 3)
-#define __NR_sync_file_range			326
+#define __NR_sync_file_range2			326
 __SYSCALL(326, sys_sync_file_range2, 6)
 #define __NR_perf_event_open			327
 __SYSCALL(327, sys_perf_event_open, 5)