iwlwifi: avoid allocating memory for region with disabled domain

In iwl_fw_ini_get_trigger_len the driver allocates space for memory
regions regardless of their domain and in iwl_fw_ini_dump_trigger the
driver aborts trigger collection of disabled domain. This diff causes
unneeded memory allocation and traling zeros in the dump file.

Solve this behavior by enforcing domain checking in
iwl_fw_ini_get_trigger_len

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