device/Kconfig: Don't allow native mode in x86_64

This option is not working so don't advertise it.

Change-Id: I910162756a567289b2484a5445360a3197ae848c
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69506
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>
diff --git a/src/device/Kconfig b/src/device/Kconfig
index a41f261..34600ad 100644
--- a/src/device/Kconfig
+++ b/src/device/Kconfig
@@ -197,7 +197,7 @@
 config PCI_OPTION_ROM_RUN_REALMODE
 	prompt "Native mode"
 	bool
-	depends on ARCH_X86
+	depends on ARCH_X86 && !ARCH_RAMSTAGE_X86_64
 	help
 	  If you select this option, PCI Option ROMs will be executed
 	  natively on the CPU in real mode. No CPU emulation is involved,