net/9p/trans_xen.c: don't inclide rwlock.h directly

rwlock.h should not be included directly.  Instead linux/splinlock.h
should be included.  One thing it does is to break the RT build.

Link: http://lkml.kernel.org/r/20180504100319.11880-1-bigeasy@linutronix.deSigned-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

net/9p/trans_xen.c

@@ -38,7 +38,6 @@
 
 #include <linux/module.h>
 #include <linux/spinlock.h>
-#include <linux/rwlock.h>
 #include <net/9p/9p.h>
 #include <net/9p/client.h>
 #include <net/9p/transport.h>