staging: gpio-mt7621: Include the right header

GPIO drivers should include <linux/gpio/driver.h> only, the
<linux/gpio.h> header is deprecated.

Cc: John Crispin <john@phrozen.org>
Cc: Zhiyong Tao <zhiyong.tao@mediatek.com>
Cc: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/mt7621-gpio/gpio-mt7621.c

@@ -9,7 +9,7 @@
 
 #include <linux/io.h>
 #include <linux/err.h>
-#include <linux/gpio.h>
+#include <linux/gpio/driver.h>
 #include <linux/module.h>
 #include <linux/of_irq.h>
 #include <linux/spinlock.h>