wifi: mac80211: do not pass a stopped vif to the driver in .get_txpower

wifi: mac80211: do not pass a stopped vif to the driver in .get_txpower

commit 393b6bc174b0dd21bb2a36c13b36e62fc3474a23 upstream.

Avoid potentially crashing in the driver because of uninitialized private data

Fixes: 5b3dc42b1b0d ("mac80211: add support for driver tx power reporting")
Cc: stable@vger.kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://patch.msgid.link/20241002095630.22431-1-nbd@nbd.name
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>