device/Kconfig: Introduce MMCONF_LENGTH

This is necessary because ASL Memory32Fixed values cannot contain
operations, even if they can be evaluated to constants. Add a sanity
check in pci_mmio_cfg.h to ensure consistency with MMCONF_BUS_NUMBER.

Change-Id: I8f0b5edf166580cc12c1363d8d6b6ef0f2854be9
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50033
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/device/Kconfig

@@ -521,6 +521,14 @@ config MMCONF_BUS_NUMBER
 	int
 	depends on MMCONF_SUPPORT
 
+config MMCONF_LENGTH
+	hex
+	depends on MMCONF_SUPPORT
+	default 0x04000000 if MMCONF_BUS_NUMBER = 64
+	default 0x08000000 if MMCONF_BUS_NUMBER = 128
+	default 0x10000000 if MMCONF_BUS_NUMBER = 256
+	default 0x0
+
 config PCI_ALLOW_BUS_MASTER
 	bool "Allow coreboot to set optional PCI bus master bits"
 	default y