rockchip: gpio: add macro so we can get gpio number

sometimes we need gpio number, so add this macro so we
can get the gpio number if we need.

BRANCH=None
BUG=chrome-os-partner:51924
TEST=Build gru

Change-Id: I98e8cf15543179904295a86e9f720c2d7c8b443a
Signed-off-by: Lin Huang <hl@rock-chips.com>
Reviewed-on: https://chromium-review.googlesource.com/349701
Commit-Ready: Douglas Anderson <dianders@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>

src/soc/rockchip/common/include/soc/gpio.h

@@ -19,6 +19,8 @@
 #include <types.h>
 
 #define GPIO(p, b, i) ((gpio_t){.port = p, .bank = GPIO_##b, .idx = i})
+#define GET_GPIO_NUM(gpio)	(gpio.port * 32 + gpio.bank * 8 + gpio.idx)
+
 
 struct rockchip_gpio_regs {
 	u32 swporta_dr;