ACPICA: Linux headers: Remove ACPI_PREEMPTION_POINT() due to no usages.

This patch deletes deprecated ACPI_PREEMPTION_POINT(), there is no user
for it in Linux kernel now.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>