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>

fs/fs_struct.c

@@ -3,6 +3,7 @@
 #include <linux/fs.h>
 #include <linux/path.h>
 #include <linux/slab.h>
+#include <linux/fs_struct.h>
 
 /*
  * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.