Get rid of indirect include of fs_struct.h

Don't pull it in sched.h; very few files actually need it and those
can include directly.  sched.h itself only needs forward declaration
of struct fs_struct;

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index afad7de..7b370c7 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -8,6 +8,7 @@
 struct uts_namespace;
 struct ipc_namespace;
 struct pid_namespace;
+struct fs_struct;
 
 /*
  * A structure to contain pointers to all per-process