[PATCH ethtool 3/3] marvell.c: Fix build with musl-libc

After commit 1fa60003a8b8 ("misc: header includes cleanup") we stopped
including net/if.h which resolved the proper defines to pull in
sys/types.h and provide a definition for u_int32_t. With musl-libc we
need to define _GNU_SOURCE to ensure that sys/types.h does provide a
definition for u_int32_t.

Fixes: 1fa60003a8b8 ("misc: header includes cleanup")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 marvell.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/marvell.c b/marvell.c
index d3d570e4d4ad..be2fc36b8fc5 100644
--- a/marvell.c
+++ b/marvell.c

@@ -6,7 +6,7 @@
  */
 
 #include <stdio.h>
-
+#define _GNU_SOURCE
 #include "internal.h"
 
 static void dump_addr(int n, const u8 *a)

-- 
2.34.1