rules.h, thread.h, lib/cbfs: Add ENV_STAGE_SUPPORTS_COOP

This change consolidates the COOP rules. Co-op in theory works in all
x86 stages now, but it hasn't been enabled yet.

BUG=b:179699789
TEST=Boot guybrush to OS and verify preloads still work

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I1197406d1d36391998b08e3076146bb2fff59d00
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59550
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
diff --git a/src/lib/cbfs.c b/src/lib/cbfs.c
index 3a044f7..d2a4b84 100644
--- a/src/lib/cbfs.c
+++ b/src/lib/cbfs.c
@@ -359,7 +359,7 @@
 	enum cb_err err;
 	struct cbfs_preload_context *context;
 
-	if (!CONFIG(CBFS_PRELOAD) || (!ENV_RAMSTAGE && !ENV_ROMSTAGE))
+	if (!CONFIG(CBFS_PRELOAD) || !ENV_STAGE_SUPPORTS_COOP)
 		return CB_ERR_ARG;
 
 	context = find_cbfs_preload_context(name);