wifi: iwlwifi: fix iwl_mvm_get_valid_rx_ant()

Fix incorrect use of _tx_ valid ant data in the function.

Fixes: 4ea1ed1d ("wifi: iwlwifi: mvm: support set_antenna()")
Signed-off-by: Daniel Gabay <daniel.gabay@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20240618200104.b7c6a320c7dc.I3092eb5275056f2162b9694e583c310c38568b2a@changeid


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