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/fs/exec.c b/fs/exec.c
index 614991b..052a961 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -53,6 +53,7 @@
 #include <linux/tracehook.h>
 #include <linux/kmod.h>
 #include <linux/fsnotify.h>
+#include <linux/fs_struct.h>
 
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>