rtems: Rename rtems_smp_get_processor_count()

Rename rtems_smp_get_processor_count() in rtems_get_processor_count().
Make rtems_get_processor_count() a function in uni-processor
configurations to enable ABI compatibility with SMP configurations.
rtems: Rename rtems_smp_get_current_processor()

Rename rtems_smp_get_current_processor() in
rtems_get_current_processor().  Make rtems_get_current_processor() a
function in uni-processor configurations to enable ABI compatibility
with SMP configurations.