ACPI / boot: Add number of legacy IRQs to debug output

Sometimes it's useful to have that when mp_config_acpi_legacy_irqs()
is called.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/x86/kernel/acpi/boot.c

@@ -1086,7 +1086,7 @@ static void __init mp_config_acpi_legacy_irqs(void)
 	mp_bus_id_to_type[MP_ISA_BUS] = MP_BUS_ISA;
 #endif
 	set_bit(MP_ISA_BUS, mp_bus_not_pci);
-	pr_debug("Bus #%d is ISA\n", MP_ISA_BUS);
+	pr_debug("Bus #%d is ISA (nIRQs: %d)\n", MP_ISA_BUS, nr_legacy_irqs());
 
 	/*
 	 * Use the default configuration for the IRQs 0-15.  Unless