MIPS: Document former use of timerfd(2) syscall number.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
index b2c7624..de6c556 100644
--- a/arch/mips/kernel/scall64-n32.S
+++ b/arch/mips/kernel/scall64-n32.S
@@ -403,7 +403,7 @@
 	PTR	sys_ioprio_get
 	PTR	compat_sys_utimensat
 	PTR	compat_sys_signalfd		/* 6280 */
-	PTR	sys_ni_syscall
+	PTR	sys_ni_syscall			/* was timerfd */
 	PTR	sys_eventfd
 	PTR	sys_fallocate
 	PTR	sys_timerfd_create