nfs: NFS_SWAP should depend on SWAP

commit 474c4f30 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: a564b8f0 ("nfs: enable swap on NFS")
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/nfs/Kconfig

@@ -89,7 +89,7 @@ config NFS_V4
 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.