ypr0: Fix erroneous if condition.

The GPIO device file wasn't closed due to this. This wasn't a big deal
because the device powers off shorty afterwards anyway.

Change-Id: I9a6b4d57d32627157323b4883e47b8812f5dcb4d

firmware/target/hosted/samsungypr/gpio_ypr.c

@@ -37,7 +37,7 @@ void gpio_init(void)
 
 void gpio_close(void)
 {
-    if (r0_gpio_dev < 0)
+    if (r0_gpio_dev >= 0)
         close(r0_gpio_dev);
 }