tty: add SPDX identifiers to Kconfig and Makefiles

There were a few Kconfig and Makefiles under drivers/tty/ that were
missing a SPDX identifier.  Fix that up so that automated tools can
properly classify all kernel source files.

Cc: Jiri Slaby <jslaby@suse.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Acked-by: David Sterba <dsterba@suse.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>