UPSTREAM: char: lack of bool string made CONFIG_DEVPORT always on

(cherry pick from commit f2cfa58b136e4b06a9b9db7af5ef62fbb5992f62)

Without a bool string present, using "# CONFIG_DEVPORT is not set" in
defconfig files would not actually unset devport. This esnured that
/dev/port was always on, but there are reasons a user may wish to
disable it (smaller kernel, attack surface reduction) if it's not being
used. Adding a message here in order to make this user visible.

Signed-off-by: Max Bires <jbires@google.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Bug: 37210310
Bug: 36604779
Change-Id: Ib1e947526f6c6f7cdf6389923287631056f32c36