NFS: unmark NFS direct I/O as experimental

Remove the EXPERIMENTAL flag from the NFS_DIRECTIO option.

Test plan:
Unset the EXPERIMENTAL kernel build option and check to see that the NFS
direct I/O option is still available.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/Kconfig

@@ -1471,8 +1471,8 @@ config NFS_V4
 	  If unsure, say N.
 
 config NFS_DIRECTIO
-	bool "Allow direct I/O on NFS files (EXPERIMENTAL)"
-	depends on NFS_FS && EXPERIMENTAL
+	bool "Allow direct I/O on NFS files"
+	depends on NFS_FS
 	help
 	  This option enables applications to perform uncached I/O on files
 	  in NFS file systems using the O_DIRECT open() flag.  When O_DIRECT