wifi: mac80211: remove an unneeded check in Rx

wifi: mac80211: remove an unneeded check in Rx

Coverity pointed out that __ieee80211_rx_h_amsdu() checks if rx->sta is
NULL before dereferencing it but not always.

Since rx->sta can't be NULL at this point, just remove the check to
avoid confusion

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250101070249.033096029d0a.I0923387246a6152f589d278f27f27bce52daee79@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>