drivers/net/enic: fix sparse warning: make symbol static

Fix this sparse warning:

  drivers/net/enic/vnic_dev.c:288:5: warning: symbol 'vnic_dev_capable' was not declared. Should it be static?

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/enic/vnic_dev.c b/drivers/net/enic/vnic_dev.c
index 08a37b0..1170857 100644
--- a/drivers/net/enic/vnic_dev.c
+++ b/drivers/net/enic/vnic_dev.c
@@ -285,7 +285,7 @@
 	return -ETIMEDOUT;
 }
 
-int vnic_dev_capable(struct vnic_dev *vdev, enum vnic_devcmd_cmd cmd)
+static int vnic_dev_capable(struct vnic_dev *vdev, enum vnic_devcmd_cmd cmd)
 {
 	u64 a0 = (u32)cmd, a1 = 0;
 	int wait = 1000;