drivers/cpuidle: Convert non-modular drivers to use builtin_platform_driver

All these drivers are configured with Kconfig options that are
declared as bool.  Hence it is not possible for the code
to be built as modular.  However the code is currently using the
module_platform_driver() macro for driver registration.

While this currently works, we really don't want to be including
the module.h header in non-modular code, which we'll be forced
to do, pending some upcoming code relocation from init.h into
module.h.  So we fix it now by using the non-modular equivalent.

Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>