lib/program_loaders.c: Mark run_ramstage with __noreturn

This allows the compiler to optimize out code called after run_ramstage.

Also remove some die() statements in soc code as run_ramstage already
has a die_with_postcode statement.

Change-Id: Id8b841712661d3257b0dc67b509f97bdc31fcf6f
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65811
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/include/program_loading.h

@@ -152,7 +152,7 @@ enum cb_err legacy_romstage_select_and_load(struct prog *romstage);
  */
 void preload_ramstage(void);
 /* Run ramstage from romstage. */
-void run_ramstage(void);
+void __noreturn run_ramstage(void);
 
 /***********************
  *   PAYLOAD LOADING   *