iwlwifi: remove false rxon if rx chain changes

Rx chain might change during power save transitions but it doesn't
require sending Full-ROXN command to the firmware. Full-RXON requires
reconnection to an AP and thus affects user experience. The patch
avoids the Full-RXON by removing the rx_chain modification check in
iwl_full_rxon_required function.

Signed-off-by: Mohamed Abbas <mohamed.abbas@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>