kernel: wifi: mac80211: don't return unset power in ieee80211_get_tx_power()

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: don't return unset power in ieee80211gettxpower We can get a UBSAN warning if ieee80211gettxpower returns the INTMIN value mac80211 internally uses for "unset power level". UBSAN: signed-integer-overflow in...