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/ntfs/super.c b/fs/ntfs/super.c
index abaaa1c..80b0477 100644
--- a/fs/ntfs/super.c
+++ b/fs/ntfs/super.c
@@ -201,8 +201,7 @@
 						v, old_nls->charset);
 				nls_map = old_nls;
 			} else /* nls_map */ {
-				if (old_nls)
-					unload_nls(old_nls);
+				unload_nls(old_nls);
 			}
 		} else if (!strcmp(p, "utf8")) {
 			bool val = false;
@@ -2427,10 +2426,9 @@
 		ntfs_free(vol->upcase);
 		vol->upcase = NULL;
 	}
-	if (vol->nls_map) {
-		unload_nls(vol->nls_map);
-		vol->nls_map = NULL;
-	}
+
+	unload_nls(vol->nls_map);
+
 	sb->s_fs_info = NULL;
 	kfree(vol);