iwlwifi: avoid collecting firmware dump if not loaded

Trying to collect firmware debug data while firmware
is not loaded causes various errors (e.g. failing NIC access).
This causes even a bigger issue if at that time the
HW radio is off.
In that case, when later turning the radio on, the Driver
fails to read the HW (registers contain garbage values).
(It may be that the CSR_GP_CNTRL_REG_FLAG_RFKILL_WAKE_L1A_EN
bit is cleared on faulty NIC access - since the same behavior
was seen in HW RFKILL toggling before setting that bit.)

Signed-off-by: Shaul Triebitz <shaul.triebitz@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>