ACPI: processor_idle: Use acpi_idle_play_dead() for all C-states

Notice that acpi_processor_setup_cstates() can set state->enter_dead to acpi_idle_play_dead() for all C-states unconditionally and remove the
confusing C-state type check done before setting it.

No intentional functional impact.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Tested-by: Mario Limonciello <mario.limonciello@amd.com> # 6.12-rc7
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/2373563.ElGaqSPkdT@rjwysocki.net