Move x86_cpu_to_apicid to the __read_mostly section

Pls., consider applying this patch series.

It contains the following changes:
- Adds two new macros DEFINE_EARLY_PER_CPU_READ_MOSTLY() and DECLARE_EARLY_PER_CPU_READ_MOSTLY().
- Adds "read-mostly" qualifier to the following variables in smp.h:
- cpu_sibling_map
- cpu_core_map
- cpu_llc_shared_map
- cpu_llc_id
- cpu_number
- x86_cpu_to_apicid
- x86_bios_cpu_apicid
- x86_cpu_to_logical_apicid

As long as all the variables above are only written during the initialization, this change is meant to prevent the false sharing and improve the performance on large multiprocessor systems.

thanks,
vlad