intel_idle: Rearrange intel_idle_cpuidle_driver_init()

Notice that intel_idle_state_table_update() only needs to be called
if icpu is not NULL, so fold it into intel_idle_init_cstates_icpu(),
and pass a pointer to the driver object to
intel_idle_cpuidle_driver_init() as an argument instead of
referencing it locally in there.

No intentional functional impact.

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