iwlagn: don't resend RXON timing

Resending RXON timing here caused issues with
dual-mode under certain circumstances, so avoid
doing it here right now.

This effectively reverts b01efe43
and partially 2491fa42. The next
patch will make all this cleaner for just the
devices that need it.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>