iwlwifi: fix problem when rf_killswitch change during suspend/resume

After we delay device initialization until interface up, there are more
conditions for the hardware rf_kill switch states during suspend and
resume. For example, before suspend we can have interface up or down,
rf_kill enable or disable; before resume we can have rf_kill enable or
disable. So there are totally 2^3 = 8 conditions to handle. This patch
addressed this problem and makes sure every condition works correctly.

This patch also merges the device suspend and resume handlers with the
mac_start and mac_stop code since they are basically doing the same
thing.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>