Fix gpio includes of mt8173 platform to avoid collision.

All files including plat/mediatek/mt8173/drivers/gpio/gpio.h were
using system includes instead of user includes, which may cause the
wrong version of the header to be included. Said includes have been
changed to user includes to make sure that the included file is the
wanted one.

Change-Id: I29bdfe96fbd9a7900875e2357bbb43f3ea431fa5

plat/mediatek/mt8173/drivers/gpio/gpio.c

@@ -28,10 +28,10 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 #include <debug.h>
-#include <gpio.h>
 #include <mmio.h>
 #include <mt8173_def.h>
 #include <pmic_wrap_init.h>
+#include "gpio.h"
 
 enum {
 	MAX_GPIO_REG_BITS = 16,

plat/mediatek/mt8173/plat_pm.c

@@ -36,7 +36,6 @@
 #include <console.h>
 #include <debug.h>
 #include <errno.h>
-#include <gpio.h>
 #include <mcucfg.h>
 #include <mmio.h>
 #include <mt8173_def.h>
@@ -49,6 +48,7 @@
 #include <spm_hotplug.h>
 #include <spm_mcdi.h>
 #include <spm_suspend.h>
+#include "drivers/gpio/gpio.h"
 
 struct core_context {
 	unsigned long timer_data[8];