x86/smpboot: Log error on secondary CPU wakeup failure at ERR level

If system is running without debug level logging,
it will not log error if do_boot_cpu() failed to
wakeup AP. It may lead to silent AP bringup
failures at boot time.
Change message level to KERN_ERR to make error
visible to user as it's done on other architectures.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1401975765-22328-3-git-send-email-imammedo@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/smpboot.c

@@ -918,7 +918,7 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
 
 	err = do_boot_cpu(apicid, cpu, tidle);
 	if (err) {
-		pr_debug("do_boot_cpu failed %d\n", err);
+		pr_err("do_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu);
 		return -EIO;
 	}