intel/apollolake_rvp: Add sleepstates.asl to dsdt

cat /sys/power/state should show supported sleep states as freeze and 
mem where freeze is "Suspend to Idle" and mem is "Suspend to RAM"

Change-Id: Ia72aaf6642dcdc9106c1992af3cf6cb21a8fff4a
Signed-off-by: Hannah Williams <hannah.williams@intel.com>
Reviewed-on: https://review.coreboot.org/14285
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/mainboard/intel/apollolake_rvp/dsdt.asl

@@ -31,4 +31,7 @@ DefinitionBlock(
 		}
 	}
 
+	/* Chipset specific sleep states */
+	#include <soc/intel/apollolake/acpi/sleepstates.asl>
+
 }