mm/page_poison.c: make early_page_poison_param() __init

The early_param() is only called during kernel initialization, So Linux
marks the function of it with __init macro to save memory.

But it forgot to mark the early_page_poison_param().  So, Make it __init
as well.

Link: http://lkml.kernel.org/r/20180117034757.27024-1-douly.fnst@cn.fujitsu.comSigned-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_poison.c

@@ -9,7 +9,7 @@
 
 static bool want_page_poisoning __read_mostly;
 
-static int early_page_poison_param(char *buf)
+static int __init early_page_poison_param(char *buf)
 {
 	if (!buf)
 		return -EINVAL;