Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index e16fb8f..273ee82 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -88,7 +88,7 @@
 static void show_type(struct seq_file *m, struct super_block *sb)
 {
 	mangle(m, sb->s_type->name);
-	if (sb->s_subtype && sb->s_subtype[0]) {
+	if (sb->s_subtype) {
 		seq_putc(m, '.');
 		mangle(m, sb->s_subtype);
 	}