soc/intel/broadwell: Define and use MMCONF_BUS_NUMBER

Note that ACPI MCFG generation reported too many busses.

Change-Id: I5acd26bac675cc818df46f60887f90b76f4580a2
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50034
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/intel/broadwell/Kconfig b/src/soc/intel/broadwell/Kconfig
index 06621f1..20254d5 100644
--- a/src/soc/intel/broadwell/Kconfig
+++ b/src/soc/intel/broadwell/Kconfig
@@ -77,9 +77,11 @@
 	select VBOOT_STARTS_IN_ROMSTAGE if !BROADWELL_VBOOT_IN_BOOTBLOCK
 
 config MMCONF_BASE_ADDRESS
-	hex
 	default 0xf0000000
 
+config MMCONF_BUS_NUMBER
+	default 64
+
 config VGA_BIOS_ID
 	string
 	default "8086,0406"