ACPI: processor: Drop duplicate setting of shared_cpu_map

'shared_cpu_map', stored as part of the per-processor
acpi_processor_performance structre, is used to store CPUs that share
a performance domain. By definition it contains the owning CPU.

While building the 'shared_cpu_map' it is being set twice - once while
initialising the performance domains and again when matching CPUs
belonging to the same domain.

Drop the unnecessary initialisation.

Signed-off-by: Punit Agrawal <punitagrawal@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>