NFS: Add COPY nfs operation

This adds the copy_range file_ops function pointer used by the
sys_copy_range() function call.  This patch only implements sync copies,
so if an async copy happens we decode the stateid and ignore it.

Signed-off-by: Anna Schumaker <bjschuma@netapp.com>
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 7fcc13c..14a762d 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -246,5 +246,6 @@
 #define NFS_CAP_DEALLOCATE	(1U << 21)
 #define NFS_CAP_LAYOUTSTATS	(1U << 22)
 #define NFS_CAP_CLONE		(1U << 23)
+#define NFS_CAP_COPY		(1U << 24)
 
 #endif