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>