iwlwifi: add num_of_sos_stats to statistics counter

When uCode detects number of beacon missed consecutively above the
internal missed beacon threshold (set by uCode), it will reset and
re-tune the radio in order to get out of bad PHY state.

This "num_of_sos_states" counter monitors number of time uCode
encounters this bad condition and has to re-tune the radio.

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