arm64/kernel: Fix return value when cpu_online() fails in __cpu_up()

If boot_secondary() was successful, and cpu_online() was an error in
__cpu_up(), -EIO was returned, but 0 is returned by commit d22b115
("arm64/kernel: Simplify __cpu_up() by bailing out early").
Therefore, bringup_wait_for_ap() causes the primary core to wait for a
long time, which may cause boot failure.
This commit sets -EIO to return code under the same conditions.

Fixes: d22b115 ("arm64/kernel: Simplify __cpu_up() by bailing out early")
Signed-off-by: Nobuhiro Iwamatsu <[email protected]>
Tested-by: Yuji Ishikawa <[email protected]>
Acked-by: Will Deacon <[email protected]>
Cc: Gavin Shan <[email protected]>
Cc: Mark Rutland <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[[email protected]: return -EIO at the end of the function]
Signed-off-by: Catalin Marinas <[email protected]>

Author: iwamatsu-t

arch/arm64/kernel/smp.c

@@ -176,7 +176,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 		panic("CPU%u detected unsupported configuration\n", cpu);
 	}
 
-	return ret;
+	return -EIO;
 }
 
 static void init_gic_priority_masking(void)