ACPI: processor: move acpi_processor_start() after acpi_processor_add()

Move acpi_processor_start() to just after acpi_processor_add().
A subsequent patch will merge them.

Code movement only; no functional change.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
CC: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
CC: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>