9p: fix bad kconfig cross-dependency

This patch moves transport dynamic registration and matching to the net
module to prevent a bad Kconfig dependency between the net and fs 9p modules.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

diff --git a/net/9p/client.c b/net/9p/client.c
index d83cc12..af91993 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -30,6 +30,7 @@
 #include <linux/sched.h>
 #include <linux/uaccess.h>
 #include <net/9p/9p.h>
+#include <linux/parser.h>
 #include <net/9p/transport.h>
 #include <net/9p/conn.h>
 #include <net/9p/client.h>