arch/x86/postcar_loader.c: Change prepare_and_run_postcar signature

The postcar frame can now be a local variable to that function.

Change-Id: I873298970fff76b9ee1cae7da156613eb557ffbc
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61964
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/drivers/amd/agesa/romstage.c

@@ -33,7 +33,6 @@ static void ap_romstage_main(void);
 
 static void romstage_main(void)
 {
-	struct postcar_frame pcf;
 	struct sysinfo romstage_state;
 	struct sysinfo *cb = &romstage_state;
 	int cbmem_initted = 0;
@@ -78,7 +77,7 @@ static void romstage_main(void)
 
 	romstage_handoff_init(cb->s3resume);
 
-	prepare_and_run_postcar(&pcf);
+	prepare_and_run_postcar();
 	/* We do not return. */
 }