fs: Make unload_nls() NULL pointer safe

Most call sites of unload_nls() do:
	if (nls)
		unload_nls(nls);

Check the pointer inside unload_nls() like we do in kfree() and
simplify the call sites.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Steve French <sfrench@us.ibm.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: Petr Vandrovec <vandrove@vc.cvut.cz>
Cc: Anton Altaparmakov <aia21@cantab.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index d79ce2e..90c5b39 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -185,8 +185,7 @@
 			cifs_sb->mountdata = NULL;
 		}
 #endif
-		if (cifs_sb->local_nls)
-			unload_nls(cifs_sb->local_nls);
+		unload_nls(cifs_sb->local_nls);
 		kfree(cifs_sb);
 	}
 	return rc;