arch/x86,lib/thread: Enable thread support in romstage

This change does the following:
* Pushes the cpu_info struct into the top of the stack (just like
  c_start.S). This is required so the cpu_info function works correctly.

* Adds the thread.c to the romstage build.

I only enabled this for romstage since I haven't done any tests in other
stages, but in theory it should work for other stages.

BUG=b:179699789
TEST=Boot guybrush with threads enabled in romstage

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I8e32e1c54dea0d0c85dd6d6753147099aa54b9b5
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56494
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
diff --git a/src/lib/Makefile.inc b/src/lib/Makefile.inc
index baf9c4d..bb3cf6a 100644
--- a/src/lib/Makefile.inc
+++ b/src/lib/Makefile.inc
@@ -149,8 +149,6 @@
 ramstage-y += edid.c
 ramstage-y += edid_fill_fb.c
 ramstage-y += memrange.c
-ramstage-$(CONFIG_COOP_MULTITASKING) += thread.c
-ramstage-$(CONFIG_TIMER_QUEUE) += timer_queue.c
 ramstage-$(CONFIG_GENERIC_GPIO_LIB) += gpio.c
 ramstage-$(CONFIG_GENERIC_UDELAY) += timer.c
 ramstage-y += b64_decode.c
@@ -160,6 +158,12 @@
 ramstage-$(CONFIG_PAYLOAD_FIT_SUPPORT) += fit.c
 ramstage-$(CONFIG_PAYLOAD_FIT_SUPPORT) += fit_payload.c
 
+romstage-$(CONFIG_TIMER_QUEUE) += timer_queue.c
+ramstage-$(CONFIG_TIMER_QUEUE) += timer_queue.c
+
+romstage-$(CONFIG_COOP_MULTITASKING) += thread.c
+ramstage-$(CONFIG_COOP_MULTITASKING) += thread.c
+
 romstage-y += cbmem_common.c
 romstage-y += imd_cbmem.c
 romstage-y += imd.c