ar71xx: drop mdio-gpio.h include from mach-om5pacv2.c

The setup code of the OpenMesh OM5P ACv2 device uses nothing
from the mdio-gpio.h header, so remove the inclusion of that.

Also remove the kernel version check which is needed only
because the mdio-gpio.h header exists in a different path
in older kernels.

Compile tested only.

Cc: Sven Eckelmann <sven.eckelmann@openmesh.com>
Signed-off-by: Gabor Juhos <juhosg@freemail.hu>

target/linux/ar71xx/files/arch/mips/ath79/mach-om5pacv2.c

@@ -11,12 +11,6 @@
  */
 
 #include <linux/gpio.h>
-#include <linux/version.h>
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4,4,0)
-#include <linux/mdio-gpio.h>
-#else
-#include <linux/platform_data/mdio-gpio.h> 
-#endif
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>
 #include <linux/platform_device.h>