iwlwifi: fw: make dump_start callback void

We never return errors there, so just make it void.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20220130115024.375b3a28d89e.Ia76e9bf13e26eb148abfebdaf859eab1b81d2af1@changeid


Signed-off-by: Luca Coelho <luciano.coelho@intel.com>