ACPI GNVS: Drop APIC, factor out MPEN

APIC was not referenced anywhere in ASL.

MPEN has references under boards:
getac/p470, roda/rk9, roda/rk886ex.

MPEN has reference also in Intel SpeedStep ASL.

Replace static MPEN with detection of multiple CPUs
installed.

Change-Id: Ib5f06416b23196b7227ccd5814162925c31c084b
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49273
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/southbridge/intel/i82801gx/lpc.c

@@ -466,8 +466,8 @@ static void lpc_final(struct device *dev)
 
 void soc_fill_gnvs(struct global_nvs *gnvs)
 {
-	gnvs->apic = 1;
-	gnvs->mpen = 1; /* Enable Multi Processing */
+	/* MPEN, Enable Multi Processing. */
+	gnvs->mpen = dev_count_cpu() > 1 ? 1 : 0;
 }
 
 static const char *lpc_acpi_name(const struct device *dev)