iwlwifi: fix for channel switch

Different channel has different configuration, need to pass correct
configuration to uCode when send "channel switch" command to uCode.
Invalid configuration will cause sysassert in uCode and produce
un-expected result.

Even it is a very small windows, but we also need to consider and handle
the case if commit_rxon occurred before the "channel switch
announcement" notification received from uCode.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>