9p: Make transports dynamic

This patch abstracts out the interfaces to underlying transports so that
new transports can be added as modules.  This should also allow kernel
configuration of transports without ifdef-hell.

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

diff --git a/net/9p/Kconfig b/net/9p/Kconfig
index 66821cd..eecbf12 100644
--- a/net/9p/Kconfig
+++ b/net/9p/Kconfig
@@ -13,6 +13,16 @@
 
 	  If unsure, say N.
 
+config NET_9P_FD
+	depends on NET_9P
+	default y if NET_9P
+	tristate "9P File Descriptor Transports (Experimental)"
+	help
+	  This builds support for file descriptor transports for 9p
+	  which includes support for TCP/IP, named pipes, or passed
+	  file descriptors.  TCP/IP is the default transport for 9p,
+	  so if you are going to use 9p, you'll likely want this.
+
 config NET_9P_DEBUG
 	bool "Debug information"
 	depends on NET_9P