use acpi.h include instead of manually adding acpi_slp_type.

Change-Id: I2a3aaf10e453fa6cce8a993356f2a0587178209a
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/276
Tested-by: build bot (Jenkins)
Reviewed-by: Uwe Hermann <uwe@hermann-uwe.de>

src/southbridge/intel/i82801gx/lpc.c

@@ -27,6 +27,7 @@
 #include <pc80/i8259.h>
 #include <arch/io.h>
 #include <arch/ioapic.h>
+#include <arch/acpi.h>
 #include <cpu/cpu.h>
 #include "i82801gx.h"
 #include <cpu/x86/smm.h>
@@ -170,8 +171,6 @@ static void i82801gx_gpi_routing(device_t dev)
 	pci_write_config32(dev, 0xb8, reg32);
 }
 
-extern u8 acpi_slp_type;
-
 static void i82801gx_power_options(device_t dev)
 {
 	u8 reg8;