src: Introduce `ARCH_ALL_STAGES_X86`

Introduce the `ARCH_ALL_STAGES_X86` Kconfig symbol to automatically
select the per-stage arch options. Subsequent commits will leverage
this to allow choosing between 32-bit and 64-bit coreboot where all
stages are x86. AMD Picasso and AMD Cezanne are the only exceptions
to this rule: they disable `ARCH_ALL_STAGES_X86` and explicitly set
the per-stage arch options accordingly.

Change-Id: Ia2ddbae8c0dfb5301352d725032f6ebd370428c9
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55759
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
diff --git a/src/arch/x86/Kconfig b/src/arch/x86/Kconfig
index 1003376..2a42a1c 100644
--- a/src/arch/x86/Kconfig
+++ b/src/arch/x86/Kconfig
@@ -28,6 +28,7 @@
 
 config ARCH_ALL_STAGES_X86_32
 	bool
+	default ARCH_ALL_STAGES_X86 && !ARCH_ALL_STAGES_X86_64
 	select ARCH_BOOTBLOCK_X86_32
 	select ARCH_VERSTAGE_X86_32
 	select ARCH_ROMSTAGE_X86_32
@@ -58,6 +59,10 @@
 	select ARCH_ROMSTAGE_X86_64
 	select ARCH_RAMSTAGE_X86_64
 
+config ARCH_ALL_STAGES_X86
+	bool
+	default y
+
 config ARCH_X86_64_PGTBL_LOC
 	hex "x86_64 page table location in CBFS"
 	depends on ARCH_BOOTBLOCK_X86_64