platform/x86: silead_dmi - abort early if DMI does not match

There is no point in registering I2C bus notifier if DMI data does not
match.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
[andy: updated due to previous patch changed]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>