fix unused parameter warning in vioc_dump_regs()

This fixes:
  external/ethtool/vioc.c:14:44: error: unused parameter 'info' [-Werror,-Wunused-parameter]
  int vioc_dump_regs(struct ethtool_drvinfo *info, struct ethtool_regs *regs)

Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I2b25a5c4d23af281616847ceb75ca8c70dfb44d0
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/vioc.c b/vioc.c
index eff533d..ef163ab 100644
--- a/vioc.c
+++ b/vioc.c
@@ -11,7 +11,8 @@
 
 #define VIOC_REGS_LINE_SIZE	sizeof(struct regs_line)
 
-int vioc_dump_regs(struct ethtool_drvinfo *info, struct ethtool_regs *regs)
+int vioc_dump_regs(struct ethtool_drvinfo *info maybe_unused,
+		   struct ethtool_regs *regs)
 {
 	unsigned int	i;
 	unsigned int	num_regs;