dell-laptop: move dell_smi_error() to dell-smbios

The dell_smi_error() method could be used by modules other than
dell-laptop for convenient translation of SMBIOS request errors into
errno values.  Thus, move it to dell-smbios.

Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>