9p: Fix setting of protocol flags in v9fs_session_info structure.

This patch fixes a simple bug I left behind in my earlier protocol
negotiation patch.

Thanks,
Sripathi.

Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>