arch: remove stage_exit()

It's no longer used. Remove it.

Change-Id: Id6f4084ab9d671e94f0eee76bf36fad9a174ef14
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13678
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/arch/x86/include/arch/stages.h

@@ -20,15 +20,4 @@
 
 void asmlinkage copy_and_run(void);
 
-static inline void stage_exit(void *entry)
-{
-	__asm__ volatile (
-#ifdef __x86_64__
-		"jmp  *%%rdi\n"
-#else
-		"jmp  *%%edi\n"
-#endif
-		:: "D"(entry)
-	);
-}
 #endif