thermal/intel_powerclamp: add __init / __exit annotations

Mark the module init / exit functions with __init / __exit accodingly.
This allows making the intel_powerclamp_ids[] array __initconst, too, as
it only gets referenced from powerclamp_probe(). This is safe as
file2alias doesn't care about the section, but the symbol name for the
MODULE_DEVICE_TABLE alias.

Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Acked-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Acked-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>