Revert "iwlwifi: assign directly to iwl_trans->cfg in QuZ detection"

This reverts commit 968dcfb4.

Both that commit and commit 809805a8
attempted to fix the same bug (dead assignments to the local variable
cfg), but they did so in incompatible ways. When they were both merged,
independently of each other, the combination actually caused the bug to
reappear, leading to a firmware crash on boot for some cards.

https://bugzilla.kernel.org/show_bug.cgi?id=205719



Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Acked-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>