Define a public predicate that defines whether a CPort ID is valid.
Use it in the message_send() routine, and make the message reported
more accurately reflect the error. Also use it to check whether the
CPort ID in a received message is valid; if it is not, just drop the
message.
Get rid of local variable "buffer" in message_send(); it adds no
value.
Signed-off-by: Alex Elder <elder@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>