RISC-V: QoS: add late_initcall to setup resctrl interface

Add late_initcall which checks if the Ssqosid extension is present, and
if so, calls resctrl setup and sets cpu hotplug state to "qos:online".

Co-developed-by: Adrien Ricciardi <aricciardi@baylibre.com>
Signed-off-by: Adrien Ricciardi <aricciardi@baylibre.com>
Signed-off-by: Drew Fustini <dfustini@baylibre.com>

arch/riscv/kernel/qos/qos.c

+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (C) 2022 Rivos Inc.
+
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/riscv_qos.h>
+
+#include <asm/csr.h>
+#include <asm/qos.h>
+
+#include "internal.h"
+
+static int __init qos_arch_late_init(void)
+{
+	int err;
+
+	if (!riscv_isa_extension_available(NULL, SSQOSID))
+		return -ENODEV;
+
+	err = qos_resctrl_setup();
+	if (err != 0)
+		return err;
+
+	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "qos:online", qos_resctrl_online_cpu,
+			  qos_resctrl_offline_cpu);
+
+	return err;
+}
+late_initcall(qos_arch_late_init);