net/sunrpc/svc_xprt.c: fix sparse warnings

Fix the following sparse warnings in net/sunrpc/svc_xprt.c.

  warning: symbol 'svc_recv' was not declared. Should it be static?
  warning: symbol 'svc_drop' was not declared. Should it be static?
  warning: symbol 'svc_send' was not declared. Should it be static?
  warning: symbol 'svc_close_all' was not declared. Should it be static?
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: NJ. Bruce Fields <bfields@citi.umich.edu>

net/sunrpc/svc_xprt.c

@@ -11,6 +11,7 @@
 #include <net/sock.h>
 #include <linux/sunrpc/stats.h>
 #include <linux/sunrpc/svc_xprt.h>
+#include <linux/sunrpc/svcsock.h>
 
 #define RPCDBG_FACILITY	RPCDBG_SVCXPRT