arm64 nexus: remove incorrect warning

acpi_config_intr() will be called when an arm64 system booted with ACPI.
We do the interrupt mapping for ACPI interrupts in nexus_acpi_map_intr()
on arm64, so acpi_config_intr() has to just return success without
printing this error message.

Reviewed by:	andrew
Differential Revision:	https://reviews.freebsd.org/D19432

sys/arm64/arm64/nexus.c

@@ -292,9 +292,11 @@ nexus_config_intr(device_t dev, int irq, enum intr_trigger trig,
     enum intr_polarity pol)
 {
 
-	/* TODO: This is wrong, it's needed for ACPI */
-	device_printf(dev, "bus_config_intr is obsolete and not supported!\n");
-	return (EOPNOTSUPP);
+	/*
+	 * On arm64 (due to INTRNG), ACPI interrupt configuration is 
+	 * done in nexus_acpi_map_intr().
+	 */
+	return (0);
 }
 
 static int