iwlwifi: mvm: consider RFKILL during INIT as success

There's no need to differentiate an INIT that ended early because of
RFKILL from one that succeded.  Additionally, if INIT fails later,
during calibration, due to RFKILL, we can just return success and
continue as if we were already in RFKILL to start with.

Remove this unnecessary differentiation and do some other small
clean-ups while at it.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>