iwlwifi: mvm: don't use ret when not initialised

fw-dbg code return ret but that variable was either 0
or not initialised. Return 0 always.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Fixes: 6a951267

 ("iwlwifi: mvm: send dbg config hcmds to fw if set in tlv")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>