arm64: Clear OSDLR_EL1 on CPU boot

mainline inclusion
from mainline-5.1
commit 6fda41bf
category: bugfix
bugzilla: 14500
CVE: NA

-------------------------------------------------

Some firmwares may reboot CPUs with OS Double Lock set. Make sure that
it is unlocked, in order to use debug exceptions.

Cc: <stable@vger.kernel.org>
Signed-off-by: NJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NHongbo Yao <yaohongbo@huawei.com>
Reviewed-by: NXuefeng Wang <wxf.wang@hisilicon.com>
Reviewed-by: NChen Zhou <chenzhou10@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arm64/kernel/debug-monitors.c

@@ -135,6 +135,7 @@ NOKPROBE_SYMBOL(disable_debug_monitors);
  */
 static int clear_os_lock(unsigned int cpu)
 {
+	write_sysreg(0, osdlr_el1);
 	write_sysreg(0, oslar_el1);
 	isb();
 	return 0;