driver: gpio: hikey: Fix pointer conversion warnings for hikey

Fix below compilation warnings-
drivers/gpio/hi6220_gpio.c: In function ‘hi6220_gpio_probe’:
drivers/gpio/hi6220_gpio.c:82:15: warning: cast to pointer from integer
of different size [-Wint-to-pointer-cast]
  bank->base = (u8 *)plat->base;

Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>

arch/arm/include/asm/arch-hi6220/gpio.h

@@ -21,7 +21,7 @@ struct gpio_bank {
 /* Information about a GPIO bank */
 struct hikey_gpio_platdata {
 	int bank_index;
-	unsigned int base;     /* address of registers in physical memory */
+	ulong base;     /* address of registers in physical memory */
 };
 
 #endif /* _HI6220_GPIO_H_ */