mlxsw: spectrum: compile-in dpipe support only if devlink is enabled

Makes no sense to have dpipe compiled in when devlink is not enabled,
because the devlink dpipe registation is noop function. So don't compile
it in. This also fixes missing extern structs errors.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: a86f0309 ("mlxsw: spectrum_dpipe: Add support for IPv4 host table dump")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/Makefile

@@ -16,8 +16,9 @@ mlxsw_spectrum-objs		:= spectrum.o spectrum_buffers.o \
 				   spectrum_switchdev.o spectrum_router.o \
 				   spectrum_kvdl.o spectrum_acl_tcam.o \
 				   spectrum_acl.o spectrum_flower.o \
-				   spectrum_cnt.o spectrum_dpipe.o \
+				   spectrum_cnt.o \
 				   spectrum_fid.o
 mlxsw_spectrum-$(CONFIG_MLXSW_SPECTRUM_DCB)	+= spectrum_dcb.o
+mlxsw_spectrum-$(CONFIG_NET_DEVLINK) += spectrum_dpipe.o
 obj-$(CONFIG_MLXSW_MINIMAL)	+= mlxsw_minimal.o
 mlxsw_minimal-objs		:= minimal.o

drivers/net/ethernet/mellanox/mlxsw/spectrum_dpipe.h

@@ -35,9 +35,24 @@
 #ifndef _MLXSW_PIPELINE_H_
 #define _MLXSW_PIPELINE_H_
 
+#if IS_ENABLED(CONFIG_NET_DEVLINK)
+
 int mlxsw_sp_dpipe_init(struct mlxsw_sp *mlxsw_sp);
 void mlxsw_sp_dpipe_fini(struct mlxsw_sp *mlxsw_sp);
 
+#else
+
+static inline int mlxsw_sp_dpipe_init(struct mlxsw_sp *mlxsw_sp)
+{
+	return 0;
+}
+
+static inline void mlxsw_sp_dpipe_fini(struct mlxsw_sp *mlxsw_sp)
+{
+}
+
+#endif
+
 #define MLXSW_SP_DPIPE_TABLE_NAME_ERIF "mlxsw_erif"
 #define MLXSW_SP_DPIPE_TABLE_NAME_HOST4 "mlxsw_host4"