dpdk: enable gso when the tap PMD is enabled

Setting DPDK_PMD_TAP=y when building will enable the tap PMD
in the build configuration that is generated for DPDK. Enabling
this currently results in a failure during compilation because
rte_gso.h is not found. RTE_LIBRTE_GSO needs to be set to y for
this to work.

Use the setting for the tap PMD to determine the value for
RTE_LIBRTE_GSO.

Change-Id: Ie395417b1c62369a95320856081ad52c674ce9f2
Signed-off-by: Matthew Smith <mgsmith@netgate.com>
diff --git a/build/external/packages/dpdk.mk b/build/external/packages/dpdk.mk
index b981ebb..82ae2d2 100644
--- a/build/external/packages/dpdk.mk
+++ b/build/external/packages/dpdk.mk
@@ -194,6 +194,7 @@
 	$(call set,RTE_LIBRTE_MLX4_DLOPEN_DEPS,$(DPDK_MLX4_PMD))
 	$(call set,RTE_LIBRTE_MLX5_DLOPEN_DEPS,$(DPDK_MLX5_PMD_DLOPEN_DEPS))
 	$(call set,RTE_LIBRTE_PMD_TAP,$(DPDK_TAP_PMD))
+	$(call set,RTE_LIBRTE_GSO,$(DPDK_TAP_PMD))
 	$(call set,RTE_LIBRTE_PMD_FAILSAFE,$(DPDK_FAILSAFE_PMD))
 	@# not needed
 	$(call set,RTE_ETHDEV_RXTX_CALLBACKS,n)
@@ -214,7 +215,6 @@
 	$(call set,RTE_LIBRTE_FLOW_CLASSIFY,n)
 	$(call set,RTE_LIBRTE_ACL,n)
 	$(call set,RTE_LIBRTE_GRO,n)
-	$(call set,RTE_LIBRTE_GSO,n)
 	$(call set,RTE_LIBRTE_KNI,n)
 	$(call set,RTE_LIBRTE_BPF,n)
 	$(call set,RTE_LIBRTE_RAWDEV,n)