greybus: fill in destination data at send time

greybus: fill in destination data at send time

For ES1 we need to insert the destination CPort id before the data
to be sent over UniPro.  Currently this is done at the time the
buffer is created, but there's no need to do so until we're actually
going to send the content of the buffer.

Move the setting of that destination information into submit_gbuf().
Note that this allows us to defer initializing a few other gbuf
fields until after we know the buffer allocation has succeeded.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>