ACPICA: Namespace: Add acpi_ns_get_node_unlocked()

ACPICA commit 3ef1a1bf5612fe1a629424c09eaaeb6f299d313c

Add acpi_ns_get_node_unlocked() to be used when ACPI_MTX_NAMESPACE is
locked. Lv Zheng.

Link: https://github.com/acpica/acpica/commit/3ef1a1bf


Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Tested-by: Greg White <gwhite@kupulau.com>
Tested-by: Dutch Guy <lucht_piloot@gmx.net>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>