arch/x86/mpspec: turn compile-time check into Kconfig dependency

Instead of checking if there is more than one PCI segment group and
erroring out in that case during the build, add this requirement as a
dependency to the GENERATE_MP_TABLE Kconfig option. The mpspec.c source
file only gets included in the build if GENERATE_MP_TABLE is selected.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Suggested-by: Martin Roth <gaumless@gmail.com>
Change-Id: Ie532a401ad0161890d0fb4ca2889af022d5f6b47
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79994
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martin.roth@amd.corp-partner.google.com>
diff --git a/src/Kconfig b/src/Kconfig
index 7867f44..21c50c5 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -906,6 +906,7 @@
 config GENERATE_MP_TABLE
 	prompt "Generate an MP table" if HAVE_MP_TABLE
 	bool
+	depends on !ECAM_MMCONF_SUPPORT || ECAM_MMCONF_BUS_NUMBER <= 256
 	default HAVE_MP_TABLE
 	help
 	  Generate an MP table (conforming to the Intel MultiProcessor