ACPI / processor: Return specific error value when mapping lapic id

Usually, 0 is returned for success in int-returning functions and
negative value are returned on failure, but in processor_core.c, some
function return 1 for success and 0 for failure which causes confusion
to happen sometimes, so modify the functions in question to follow the
common convention..

Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
[rjw: Changelog]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>