ACPI / processor: remove some dead code in acpi_processor_get_info()

errata.smp is used by nowhere, so the variable assignment is meanless,
remove it.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>