9p: fix flags length in net

Some files in the net/9p directory uses "int" for flags. This can
cause hard to find bugs on some architectures. This patch converts the
flags to use "long" instead.

This bug was discovered by doing an allyesconfig make on the -rt kernel
where checks are done to ensure all flags are of size sizeof(long).

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Acked-by: Eric Van Hensbergen <ericvh@gmail.com>