wifi: iwlwifi: mld: avoid panic on init failure

In the Linux kernel, the following vulnerability has been resolved:

wifi: iwlwifi: mld: avoid panic on init failure

In case of an error during init, in_hw_restart will be set, but it will
never get cleared.
Instead, we will retry to init again, and then we will act like we are in a
restart when we are actually not.

This causes (among others) to a NULL pointer dereference when canceling
rx_omi::finished_work, that was not even initialized, because we thought
that we are in hw_restart.

Set in_hw_restart to true only if the fw is running, then we know that
FW was loaded successfully and we are not going to the retry loop.