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>