soc/amd: Add "halt this AP" callback to romstage

As part of moving AGESA calls from bootblock to romstage, callback function
AGESA_HALT_THIS_AP must be available at romstage.

BUG=b:74236170
TEST=Build and boot grunt, actual test will be performed at a later patch.

Change-Id: I0992b2de5856881c19191ec4f637168727686524
Signed-off-by: Richard Spiegel <richard.spiegel@silverbackltd.com>
Reviewed-on: https://review.coreboot.org/25527
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/amd/common/block/pi/def_callouts.c b/src/soc/amd/common/block/pi/def_callouts.c
index beb2d18..fec1776 100644
--- a/src/soc/amd/common/block/pi/def_callouts.c
+++ b/src/soc/amd/common/block/pi/def_callouts.c
@@ -35,6 +35,9 @@
 #else
 const BIOS_CALLOUT_STRUCT BiosCallouts[] = {
 	/* Required callouts */
+#if ENV_ROMSTAGE
+	{ AGESA_HALT_THIS_AP,             agesa_HaltThisAp },
+#endif
 	{ AGESA_ALLOCATE_BUFFER,          agesa_AllocateBuffer },
 	{ AGESA_DEALLOCATE_BUFFER,        agesa_DeallocateBuffer },
 	{ AGESA_DO_RESET,                 agesa_Reset },