platform/x86: acerhdf: mark appropriate content with __init prefix

These three functions are only called from the probe code which is
already marked __init and hence these can be __init as well.

Cc: Peter Feuerer <peter@piie.net>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Andy Shevchenko <andy@infradead.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Peter Feuerer <peter@piie.net>