soc/cavium/cn81xx/Kconfig: specify ECAM_MMCONF_BUS_NUMBER

The Cavium CN81xx SoC selects ECAM_MMCONF_SUPPORT, but doesn't set a
value for ECAM_MMCONF_BUS_NUMBER which results in it defaulting to 0
which is wrong. Both the Cavium CN8100 SFF EVB and the OpenCellular
Elgon (GBCv2) mainboard specify 32 PCI buses in their Linux devicetree
files, so set the SoC's ECAM_MMCONF_BUS_NUMBER Kconfig option to 32 to
match this.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Suggested-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Change-Id: Ic98381e2cc597cf23af249c71911545692e40f64
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79931
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Patrick Rudolph <patrick.rudolph@9elements.com>

src/soc/cavium/cn81xx/Kconfig

@@ -39,4 +39,7 @@ config STACK_SIZE
 config ECAM_MMCONF_BASE_ADDRESS
 	default 0x848000000000
 
+config ECAM_MMCONF_BUS_NUMBER
+	default 32
+
 endif