src/: Replace some __PRE_RAM__ use

Change-Id: Iaa56e7b98aad33eeb876edd7465c56c80fd1ac18
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35398
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/include/thread.h

@@ -20,7 +20,7 @@
 #include <bootstate.h>
 #include <arch/cpu.h>
 
-#if CONFIG(COOP_MULTITASKING) && !defined(__SMM__) && !defined(__PRE_RAM__)
+#if ENV_RAMSTAGE && CONFIG(COOP_MULTITASKING)
 
 struct thread {
 	int id;