9p: disallow RDMA if RDMA CM isn't available

If INET=y and INFINIBAND=y, but IPV6=m then INFINIBAND_ADDR_TRANS is set
to n and the RDMA CM functions rdma_connect() et al are not built.
However, the current config dependencies allow NET_9P_RDMA to be selected
in this, which leads to a build failure. Fix this by adding a dependency
on INFINIBAND_ADDR_TRANS to disallow NET_9P_RDMA in this case.

Reported-by: Randy Dunlap <[e-mail]>
Signed-off-by: Roland Dreier <[e-mail]>
Acked-by: Randy Dunlap <[e-mail]>
Tested-by: Randy Dunlap <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

net/9p/Kconfig

···
 	  guest partitions and a host partition.
 
 config NET_9P_RDMA
-	depends on INET && INFINIBAND && EXPERIMENTAL
+	depends on INET && INFINIBAND && INFINIBAND_ADDR_TRANS && EXPERIMENTAL
 	tristate "9P RDMA Transport (Experimental)"
 	help
 	  This builds support for an RDMA transport.