net: tso: Export symbols for modular build

Export the symbols to fix the below errors when built as modules:
ERROR: "tso_build_data" [drivers/net/ethernet/marvell/mvneta.ko] undefined!
ERROR: "tso_build_hdr" [drivers/net/ethernet/marvell/mvneta.ko] undefined!
ERROR: "tso_start" [drivers/net/ethernet/marvell/mvneta.ko] undefined!
ERROR: "tso_count_descs" [drivers/net/ethernet/marvell/mvneta.ko] undefined!
ERROR: "tso_build_data" [drivers/net/ethernet/marvell/mv643xx_eth.ko] undefined!
ERROR: "tso_build_hdr" [drivers/net/ethernet/marvell/mv643xx_eth.ko] undefined!
ERROR: "tso_start" [drivers/net/ethernet/marvell/mv643xx_eth.ko] undefined!
ERROR: "tso_count_descs" [drivers/net/ethernet/marvell/mv643xx_eth.ko] undefined!
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/tso.c

+#include <linux/export.h>
 #include <net/ip.h>
 #include <net/tso.h>
 
@@ -7,6 +8,7 @@ int tso_count_descs(struct sk_buff *skb)
 	/* The Marvell Way */
 	return skb_shinfo(skb)->gso_segs * 2 + skb_shinfo(skb)->nr_frags;
 }
+EXPORT_SYMBOL(tso_count_descs);
 
 void tso_build_hdr(struct sk_buff *skb, char *hdr, struct tso_t *tso,
 		   int size, bool is_last)
@@ -31,6 +33,7 @@ void tso_build_hdr(struct sk_buff *skb, char *hdr, struct tso_t *tso,
 		tcph->rst = 0;
 	}
 }
+EXPORT_SYMBOL(tso_build_hdr);
 
 void tso_build_data(struct sk_buff *skb, struct tso_t *tso, int size)
 {
@@ -48,6 +51,7 @@ void tso_build_data(struct sk_buff *skb, struct tso_t *tso, int size)
 		tso->next_frag_idx++;
 	}
 }
+EXPORT_SYMBOL(tso_build_data);
 
 void tso_start(struct sk_buff *skb, struct tso_t *tso)
 {
@@ -70,3 +74,4 @@ void tso_start(struct sk_buff *skb, struct tso_t *tso)
 		tso->next_frag_idx++;
 	}
 }
+EXPORT_SYMBOL(tso_start);