cpu/intel/speedstep: Emit PPKG object for first package

Tested on Lenovo Thinkpad T500.

Change-Id: I89f1ab4be338841463fb95ac75d794103380d16f
Signed-off-by: Nico Huber <nico.h@gmx.de>
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/21325
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/cpu/intel/speedstep/acpi.c

@@ -161,4 +161,7 @@ void generate_cpu_entries(device_t device)
 			acpigen_pop_len();
 		}
 	}
+	/* PPKG is usually used for thermal management
+	   of the first and only package. */
+	acpigen_write_processor_package("PPKG", 0, cores_per_package);
 }