kcore: fix /proc/kcore's stat.st_size

In 9063c61fd5cbd ("x86, 64-bit: Clean up user address masking") Linus
fixed the wrong size of /proc/kcore problem.

But its size still looks insane, since it never equals the size of
physical memory.

Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Tao Ma <tao.ma@oracle.com>
Cc: <mtk.manpages@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/kcore.c

@@ -374,9 +374,6 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 static int __init proc_kcore_init(void)
 {
 	proc_root_kcore = proc_create("kcore", S_IRUSR, NULL, &proc_kcore_operations);
-	if (proc_root_kcore)
-		proc_root_kcore->size =
-				(size_t)high_memory - PAGE_OFFSET + PAGE_SIZE;
 	return 0;
 }
 module_init(proc_kcore_init);