iwlwifi: dbg_ini: in case of region dump failure set memory to 0

In case the driver fails to dump a memory region, and this is the last
region, then partial region would be extracted.

Solve this by setting the data to zero in case of failure.
This will cause dump to be a list of consecutive successful memory
regions and trailing zeros with no partial memories extracted.

Signed-off-by: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>