mb/intel/wtm2/Kconfig: Limit MAX_CPUS to 8

Haswell and Broadwell have at most 8 threads.

Change-Id: Idcccf22addb6e15d7c55b9816141af47d6186cca
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46952
Reviewed-by:  Felix Singer <felixsinger@posteo.net>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/intel/wtm2/Kconfig

@@ -28,7 +28,7 @@ config MAINBOARD_PART_NUMBER
 
 config MAX_CPUS
 	int
-	default 16
+	default 8
 
 config VGA_BIOS_FILE
 	string