NFS: Always enable NFS direct I/O

Since O_DIRECT is a standard feature that is enabled in most distros,
eliminate the CONFIG_NFS_DIRECTIO build option, and change the
fs/nfs/Makefile to always build in the NFS direct I/O engine.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
index df0f41e..ac6170c 100644
--- a/fs/nfs/Makefile
+++ b/fs/nfs/Makefile
@@ -5,7 +5,7 @@
 obj-$(CONFIG_NFS_FS) += nfs.o
 
 nfs-y 			:= client.o dir.o file.o getroot.o inode.o super.o nfs2xdr.o \
-			   pagelist.o proc.o read.o symlink.o unlink.o \
+			   direct.o pagelist.o proc.o read.o symlink.o unlink.o \
 			   write.o namespace.o mount_clnt.o
 nfs-$(CONFIG_ROOT_NFS)	+= nfsroot.o
 nfs-$(CONFIG_NFS_V3)	+= nfs3proc.o nfs3xdr.o
@@ -14,5 +14,4 @@
 			   delegation.o idmap.o \
 			   callback.o callback_xdr.o callback_proc.o \
 			   nfs4namespace.o
-nfs-$(CONFIG_NFS_DIRECTIO) += direct.o
 nfs-$(CONFIG_SYSCTL) += sysctl.o