arch/x86: Mark prepare_and_run_postcar noreturn

This moves the die() statement to a common place.

Change-Id: I24c9f00bfee169b4ca57b469c089188ec62ddada
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65812
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/arch/x86/include/arch/romstage.h

@@ -43,7 +43,7 @@ void fill_postcar_frame(struct postcar_frame *pcf);
  * prepare_and_run_postcar() determines the stack to use after
  * cache-as-ram is torn down as well as the MTRR settings to use.
  */
-void prepare_and_run_postcar(void);
+void __noreturn prepare_and_run_postcar(void);
 
 /*
  * Systems without a native coreboot cache-as-ram teardown may implement

src/arch/x86/postcar_loader.c

@@ -63,7 +63,7 @@ static void run_postcar_phase(struct postcar_frame *pcf);
 
 /* prepare_and_run_postcar() determines the stack to use after
  * cache-as-ram is torn down as well as the MTRR settings to use. */
-void prepare_and_run_postcar(void)
+void __noreturn prepare_and_run_postcar(void)
 {
 	struct postcar_frame pcf;
 
@@ -76,6 +76,7 @@ void prepare_and_run_postcar(void)
 
 	run_postcar_phase(&pcf);
 	/* We do not return here. */
+	die("Failed to load postcar\n!");
 }
 
 static void finalize_load(uintptr_t *reloc_params, uintptr_t mtrr_frame_ptr)

src/cpu/intel/car/romstage.c

@@ -54,5 +54,4 @@ void __noreturn romstage_main(void)
 
 	prepare_and_run_postcar();
 	/* We do not return here. */
-	die("failed to load postcar\n");
 }

src/drivers/amd/agesa/romstage.c

@@ -76,7 +76,6 @@ void __noreturn romstage_main(void)
 
 	prepare_and_run_postcar();
 	/* We do not return. */
-	die("failed to load postcar\n");
 }
 
 static void ap_romstage_main(void)

src/soc/amd/stoneyridge/romstage.c

@@ -119,7 +119,6 @@ void __noreturn romstage_main(void)
 
 	post_code(0x44);
 	prepare_and_run_postcar();
-	die("failed to load postcar\n");
 }
 
 void fill_postcar_frame(struct postcar_frame *pcf)