soc/amd/picasso: move MAX_CPUS setting from mainboard to SoC Kconfig

Since the mainboard Kconfig is sourced before the SoC one, it would
still be possible to override this setting at mainboard level, even
though that shouldn't be needed. The maximum CPU count for Picasso is 8,
since the chips have only up to 4 cores with up to two threads each.

Change-Id: I53449b8fa73c5d13e6ea77bee6eed8896b7d3ec3
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47205
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/amd/mandolin/Kconfig

@@ -52,10 +52,6 @@ config DEVICETREE
 	string
 	default "variants/\$(CONFIG_VARIANT_DIR)/devicetree.cb"
 
-config MAX_CPUS
-	int
-	default 8
-
 config ONBOARD_VGA_IS_PRIMARY
 	bool
 	default y

src/mainboard/google/zork/Kconfig

@@ -96,10 +96,6 @@ config MAINBOARD_FAMILY
 	string
 	default "Google_Zork"
 
-config MAX_CPUS
-	int
-	default 8
-
 config ONBOARD_VGA_IS_PRIMARY
 	bool
 	default y

src/soc/amd/picasso/Kconfig

@@ -193,6 +193,10 @@ config VERSTAGE_ADDR
 	hex
 	default 0x4000000
 
+config MAX_CPUS
+	int
+	default 8
+
 config VGA_BIOS_ID
 	string
 	default "1002,15d8,c1"