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>

src/Kconfig

@@ -906,6 +906,7 @@ menu "System tables"
 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

src/arch/x86/mpspec.c

@@ -14,10 +14,6 @@
 #include <stdint.h>
 #include <string.h>
 
-#if CONFIG(ECAM_MMCONF_SUPPORT) && PCI_SEGMENT_GROUP_COUNT > 1
-#error "MPTable doesn't support systems with multiple PCI segment groups"
-#endif
-
 /* Initialize the specified "mc" struct with initial values. */
 void mptable_init(struct mp_config_table *mc)
 {