arm64: debug: convert OS lock CPU hotplug notifier to new infrastructure

The arm64 debug monitor initialisation code uses a CPU hotplug notifier
to clear the OS lock when CPUs come online.

This patch converts the code to the new hotplug mechanism.

Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 3758fe6..8c999a2 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -45,6 +45,7 @@
 	CPUHP_AP_PERF_METAG_STARTING,
 	CPUHP_AP_MIPS_OP_LOONGSON3_STARTING,
 	CPUHP_AP_ARM_VFP_STARTING,
+	CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
 	CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING,
 	CPUHP_AP_PERF_ARM_STARTING,
 	CPUHP_AP_ARM_L2X0_STARTING,