wifi: mac80211: Drop not needed check for NULL

ieee80211_get_txq() can only be called with vif != NULL.
Remove not needed NULL test in function.

Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/20221107161328.2883-1-alexander@wetzel-home.de


Signed-off-by: Johannes Berg <johannes.berg@intel.com>