x86 mpparse: build fix

fix this build bug:

 drivers/acpi/pci_irq.c: In function 'acpi_pci_irq_enable':
 drivers/acpi/pci_irq.c:574: error: implicit declaration of function 'mp_config_acpi_gsi'
Signed-off-by: NIngo Molnar <mingo@elte.hu>

include/asm-x86/acpi.h

@@ -28,6 +28,7 @@
 #include <asm/numa.h>
 #include <asm/processor.h>
 #include <asm/mmu.h>
+#include <asm/mpspec.h>
 
 #define COMPILER_DEPENDENT_INT64   long long
 #define COMPILER_DEPENDENT_UINT64  unsigned long long