hw/arm/stellaris: Use qemu_log_mask(UNIMP) instead of fprintf

Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Message-id: 20180624040609.17572-11-f4bug@amsat.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/arm/stellaris.c

@@ -560,7 +560,7 @@ static void ssys_write(void *opaque, hwaddr offset,
     case 0x040: /* SRCR0 */
     case 0x044: /* SRCR1 */
     case 0x048: /* SRCR2 */
-        fprintf(stderr, "Peripheral reset not implemented\n");
+        qemu_log_mask(LOG_UNIMP, "Peripheral reset not implemented\n");
         break;
     case 0x054: /* IMC */
         s->int_mask = value & 0x7f;