9p: fix endian issues [attempt 3]

When the changes were done to the protocol last release, some endian
bugs crept in.  This patch fixes those endian problems and has been
verified to run on 32/64 bit and x86/ppc architectures.

This version of the patch incorporates the correct annotations
for endian variables.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>