MIPS: 32-bit: Fix number of argument to epoll_wait.

The number of arguments only matters for syscalls with stack arguments that
is using 5 or more argument slots so this is just cosmetic fix.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/kernel/scall32-o32.S

@@ -496,7 +496,7 @@ einval:	li	v0, -ENOSYS
 	sys	sys_lookup_dcookie	4
 	sys	sys_epoll_create	1
 	sys	sys_epoll_ctl		4
-	sys	sys_epoll_wait		3	/* 4250 */
+	sys	sys_epoll_wait		4	/* 4250 */
 	sys	sys_remap_file_pages	5
 	sys	sys_set_tid_address	1
 	sys	sys_restart_syscall	0