iwlwifi: mvm: don't attempt debug collection in rfkill

If we fail to initialize because rfkill is enabled, then trying
to do debug collection currently just fails. Prevent that in the
high-level code, although we should probably also fix the lower
level code to do things more carefully.

It's not 100% clear that it fixes this commit, as the original
dump code at the time might've been more careful. In any case,
we don't really need to dump anything in this expected scenario.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Fixes: 71256480 ("iwlwifi: add fw dump upon RT ucode start failure")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>