iwlwifi: mvm: fix wrong offset while reading from NVM

As part of thermal throttling, some data is being read from NVM.
The offset is in words, but was addressed as in octets. fixed.

Signed-off-by: Eytan Lifshitz <eytan.lifshitz@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>