iwlwifi: pcie: fix command completion name debug

When the command name is printed on command completion, the wrong
group is used, leading to the wrong name being printed. Fix this
by using the group ID without inappropriately mangling it through
iwl_cmd_groupid() - it's already a u8. Also, while at it, use it
from the same place as the command ID, everything else is just
confusing.

Fixes: ab02165c ("iwlwifi: add wide firmware command infrastructure for TX")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>