nfs: NFS_SWAP should depend on SWAP

commit 474c4f306eefbb21b67ebd1de802d005c7d7ecdc upstream.

If CONFIG_SWAP=n, it does not make much sense to offer the user the
option to enable support for swapping over NFS, as that will still fail
at run time:

    # swapon /swap
    swapon: /swap: swapon failed: Function not implemented

Fix this by adding a dependency on CONFIG_SWAP.

Fixes: a564b8f0398636ba ("nfs: enable swap on NFS")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
index b1daeaf..c342876 100644
--- a/fs/nfs/Kconfig
+++ b/fs/nfs/Kconfig
@@ -89,7 +89,7 @@
 config NFS_SWAP
 	bool "Provide swap over NFS support"
 	default n
-	depends on NFS_FS
+	depends on NFS_FS && SWAP
 	select SUNRPC_SWAP
 	help
 	  This option enables swapon to work on files located on NFS mounts.