hw/gpio/omap_gpio: Replace fprintf() by qemu_log_mask(GUEST_ERROR)

Replace fprintf() by qemu_log_mask(LOG_GUEST_ERROR).

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200901104234.92159-2-f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

hw/gpio/omap_gpio.c

@@ -392,8 +392,10 @@ static void omap2_gpio_module_write(void *opaque, hwaddr addr,
         break;
 
     case 0x10:	/* GPIO_SYSCONFIG */
-        if (((value >> 3) & 3) == 3)
-            fprintf(stderr, "%s: bad IDLEMODE value\n", __func__);
+        if (((value >> 3) & 3) == 3) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "%s: Illegal IDLEMODE value: 3\n", __func__);
+        }
         if (value & 2)
             omap2_gpio_module_reset(s);
         s->config[0] = value & 0x1d;