platform/x86: dell-laptop: Handle return error form dell_get_intensity.

Here, This patch is to handle a return error from dell_get_intensity.
This change is done using Coccinelle.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>