kboot: Add missing license to termios

I neglected to include the proper license markings on these
files. Remedy that now.

Sponsored by:		Netflix

stand/kboot/arch/amd64/termios_arch.h

@@ -1 +1,7 @@
+/*-
+ * Copyright (c) 2022, Netflix, Inc.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
 #include "termios_gen.h"

stand/kboot/arch/powerpc64/termios_arch.h

@@ -1,3 +1,11 @@
+/*
+ * Copyright (c) 2005-2020 Rich Felker, et al.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Note: From the musl project, stripped down and repackaged with HOST_/host_ prepended
+ */
+
 #undef HOST_NCCS
 #define HOST_NCCS 19
 struct host_termios {

stand/kboot/termios_gen.h

@@ -1,3 +1,11 @@
+/*
+ * Copyright (c) 2005-2020 Rich Felker, et al.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Note: From the musl project, stripped down and repackaged with HOST_/host_ prepended
+ */
+
 struct host_termios {
 	host_tcflag_t c_iflag;
 	host_tcflag_t c_oflag;