nfp: add MAY_USE_DEVLINK dependency

Fix build with DEVLINK=m and NFP=y.

Fixes: 1851f93f ("nfp: add devlink support")
Reported-by: Nkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/Kconfig

@@ -19,6 +19,7 @@ config NFP
 	tristate "Netronome(R) NFP4000/NFP6000 NIC driver"
 	depends on PCI && PCI_MSI
 	depends on VXLAN || VXLAN=n
+	depends on MAY_USE_DEVLINK
 	---help---
 	  This driver supports the Netronome(R) NFP4000/NFP6000 based
 	  cards working as a advanced Ethernet NIC.  It works with both