apollolake: Define MAX_CPUS at SoC scope

The three Intel Apollo Lake boards (apl_rvp, leafhill and minnow3) do
not define MAX_CPUS, which would then default to 1. Since this is most
likely an oversight, use the same value as other Apollo Lake boards.

To ensure this does not happen again, factor out MAX_CPUS to SoC scope.

Change-Id: I5ed98a6b592c8010b59eca7ff773ae1ccc4cd7b1
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45144
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Mario Scheithauer <mario.scheithauer@siemens.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/intel/apollolake/Kconfig b/src/soc/intel/apollolake/Kconfig
index f5d9323..a30333b 100644
--- a/src/soc/intel/apollolake/Kconfig
+++ b/src/soc/intel/apollolake/Kconfig
@@ -110,7 +110,7 @@
 
 config MAX_CPUS
 	int
-	default 4 if SOC_INTEL_GEMINILAKE
+	default 4
 
 config CHROMEOS
 	select CHROMEOS_RAMOOPS_DYNAMIC