nfsd: Drop including client's header file nfs_fs.h

nfs_fs.h is a client's header file.

# ll fs/nfsd/nfs4acl.o fs/nfsd/nfsd.ko
-rw-r--r--. 1 root root 328248 Jul 3 19:26 fs/nfsd/nfs4acl.o
-rw-r--r--. 1 root root 7452016 Jul 3 19:26 fs/nfsd/nfsd.ko

After this patch,
# ll fs/nfsd/nfs4acl.o fs/nfsd/nfsd.ko
-rw-r--r--. 1 root root 150872 Jul 3 19:15 fs/nfsd/nfs4acl.o
-rw-r--r--. 1 root root 7273792 Jul 3 19:23 fs/nfsd/nfsd.ko

Signed-off-by: Kinglong Mee <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/nfsd/nfs4acl.c

···
  *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <linux/fs.h>
 #include <linux/slab.h>
-#include <linux/nfs_fs.h>
+#include <linux/posix_acl.h>
+
 #include "nfsfh.h"
 #include "nfsd.h"
 #include "acl.h"