init: remove obsolete arch_call_rest_init() wrapper

Since commit 3570ee0 ("s390/smp: keep the original lowcore for
CPU 0"), there is no longer any architecture that needs to override
arch_call_rest_init().

Remove the weak wrapper around rest_init(), call rest_init() directly, and
make rest_init() static.

Link: https://lkml.kernel.org/r/aa10868bfb176eef4abb8bb4a710b85330792694.1706106183.git.geert@linux-m68k.org
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/start_kernel.h

@@ -9,7 +9,5 @@
    up something else. */
 
 extern asmlinkage void __init __noreturn start_kernel(void);
-extern void __init __noreturn arch_call_rest_init(void);
-extern void __ref __noreturn rest_init(void);
 
 #endif /* _LINUX_START_KERNEL_H */

init/main.c

@@ -681,7 +681,7 @@ static void __init setup_command_line(char *command_line)
 
 static __initdata DECLARE_COMPLETION(kthreadd_done);
 
-noinline void __ref __noreturn rest_init(void)
+static noinline void __ref __noreturn rest_init(void)
 {
 	struct task_struct *tsk;
 	int pid;
@@ -822,11 +822,6 @@ static int __init early_randomize_kstack_offset(char *buf)
 early_param("randomize_kstack_offset", early_randomize_kstack_offset);
 #endif
 
-void __init __weak __noreturn arch_call_rest_init(void)
-{
-	rest_init();
-}
-
 static void __init print_unknown_bootoptions(void)
 {
 	char *unknown_options;
@@ -1069,7 +1064,7 @@ void start_kernel(void)
 	kcsan_init();
 
 	/* Do the rest non-__init'ed, we're now alive */
-	arch_call_rest_init();
+	rest_init();
 
 	/*
 	 * Avoid stack canaries in callers of boot_init_stack_canary for gcc-10

tools/objtool/noreturns.h

@@ -12,7 +12,6 @@ NORETURN(__reiserfs_panic)
 NORETURN(__stack_chk_fail)
 NORETURN(__tdx_hypercall_failed)
 NORETURN(__ubsan_handle_builtin_unreachable)
-NORETURN(arch_call_rest_init)
 NORETURN(arch_cpu_idle_dead)
 NORETURN(bch2_trans_in_restart_error)
 NORETURN(bch2_trans_restart_error)