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

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

This reverts commit 968dcfb4905245dc64d65312c0d17692fa087b99.

Both that commit and commit 809805a820c6445f7a701ded24fdc6bbc841d1e4
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>