gpio: dwapb: fix pointer to integer cast

The statements BUG_ON(ctx == 0) was implicitly casting a pointer
to an integer for comparison. Do this with a bool test instead
to get away from sparse warnings.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-dwapb.c

@@ -626,7 +626,7 @@ static int dwapb_gpio_suspend(struct device *dev)
 		unsigned int idx = gpio->ports[i].idx;
 		struct dwapb_context *ctx = gpio->ports[i].ctx;
 
-		BUG_ON(ctx == 0);
+		BUG_ON(!ctx);
 
 		offset = GPIO_SWPORTA_DDR + idx * GPIO_SWPORT_DDR_SIZE;
 		ctx->dir = dwapb_read(gpio, offset);
@@ -668,7 +668,7 @@ static int dwapb_gpio_resume(struct device *dev)
 		unsigned int idx = gpio->ports[i].idx;
 		struct dwapb_context *ctx = gpio->ports[i].ctx;
 
-		BUG_ON(ctx == 0);
+		BUG_ON(!ctx);
 
 		offset = GPIO_SWPORTA_DR + idx * GPIO_SWPORT_DR_SIZE;
 		dwapb_write(gpio, offset, ctx->data);