net: phy: marvell: Add a missing errno.h header

This corrects a build error on zynqmp.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/net/phy/marvell.c

@@ -8,6 +8,7 @@
  */
 #include <config.h>
 #include <common.h>
+#include <errno.h>
 #include <phy.h>
 
 #define PHY_AUTONEGOTIATE_TIMEOUT 5000