greybus: move versioning from svc message header to handshake function

greybus: move versioning from svc message header to handshake function

The Greybus spec has been updated to improve the efficiency of the
version major/minor information that had been previously carried in
every SVC message header. The version major/minor is now provided
as part of the handshake function.

Update the SVC msg header and handshake function payload definitions
and move the version major/minor validation into the SVC handshake
handling routine.

Signed-off-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>