southbridge/intel/bd82x6x: Use common gpio.c

Use shared gpio code from common folder.
Bd82x6x's gpio.c and gpio.h is used by other southbridges
as well and will be removed once it is unused.

Change-Id: I8bd981c4696c174152cf41caefa6c083650d283a
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/13614
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/mainboard/google/link/mainboard.c

@@ -32,6 +32,7 @@
 #include "onboard.h"
 #include "ec.h"
 #include <southbridge/intel/bd82x6x/pch.h>
+#include <southbridge/intel/common/gpio.h>
 #include <smbios.h>
 #include <device/pci.h>
 #include <ec/google/chromeec/ec.h>