platform/x86: hp_accel: Use SIMPLE_DEV_PM_OPS() for PM ops

platform/x86: hp_accel: Use SIMPLE_DEV_PM_OPS() for PM ops

After the commit 34570a898eef ("platform/x86: hp_accel: Remove
_INI method call") there is no need to have separate methods for
resume and restore, hence we may fold them together and use
SIMPLE_DEV_PM_OPS() for PM ops.

While at it, switch to use __maybe_unused attribute.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20211206151521.22578-1-andriy.shevchenko@linux.intel.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>