fs/nsfs.c: include headers for missing declarations

Include linux/proc_fs.h and fs/internal.h to address the following
'sparse' warnings:

    fs/nsfs.c:41:32: warning: symbol 'ns_dentry_operations' was not declared. Should it be static?
    fs/nsfs.c:145:5: warning: symbol 'open_related_ns' was not declared. Should it be static?

Link: http://lkml.kernel.org/r/20191209234822.156179-1-ebiggers@kernel.orgSigned-off-by: Eric Biggers <ebiggers@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nsfs.c

@@ -3,6 +3,7 @@
 #include <linux/pseudo_fs.h>
 #include <linux/file.h>
 #include <linux/fs.h>
+#include <linux/proc_fs.h>
 #include <linux/proc_ns.h>
 #include <linux/magic.h>
 #include <linux/ktime.h>
@@ -11,6 +12,8 @@
 #include <linux/nsfs.h>
 #include <linux/uaccess.h>
 
+#include "internal.h"
+
 static struct vfsmount *nsfs_mnt;
 
 static long ns_ioctl(struct file *filp, unsigned int ioctl,