MFC r318001:

[iwm] include opt_iwm.h and opt_wlan.h consistently in all files.

MFC r318214:

[iwm] Sanity check channel for IEEE80211_CHAN_ANYC in if_iwm_mac_ctxt.c.

* This avoids panicing in some broken vap state handling cases.

MFC r318005:

[iwm] Add basic powermanagement support via ifconfig wlan0 powersave.

* The DEVICE_POWER_FLAGS_CAM_MSK flag was removed in the upstream iwlwifi
in Linux commit ceef91c89480dd18bb3ac51e91280a233d0ca41f.

* Add sc_ps_disabled flag to struct iwm_softc, which corresponds to
mvm->ps_disabled in struct iwl_mvm in Linux iwlwifi.

* Adds a hw.iwm.power_scheme tunable which corresponds to the power_scheme
module parameter in Linux iwlwifi. Set this to 1 for completely
disabling power management, 2 (default) for balanced powermanagement,
and 3 for lowerpower mode (which does dtim period skipping).

* Imports the constants.h file from iwlwifi as if_iwm_constants.h.

* This doesn't allow changing the powermanagement setting while connected,
also one can only choose between enabled and disabled powersaving with
ifconfig (so switching between balanced and low-power mode requires
rebooting to change the tunable).

* After any changes to powermanagement (i.e. "ifconfig wlan0 powersave" to
enable powermanagement, or "ifconfig wlan0 -powersave" for disabling
powermanagement), one has to disconnect and reconnect to the accespoint
for the change to take effect.

MFC r315780:

[iwm] Remove a couple of unneeded IWM_UCODE_TLV_FLAGS_* flags.

* All the supported firmwares have these flags set.

* This removes the following flags:
IWM_UCODE_TLV_FLAGS_PM_CMD_SUPPORT,
IWM_UCODE_TLV_FLAGS_NEWBT_COEX,
IWM_UCODE_TLV_FLAGS_BF_UPDATED,
IWM_UCODE_TLV_FLAGS_D3_CONTINUITY_API,
IWM_UCODE_TLV_FLAGS_STA_KEY_CMD,
IWM_UCODE_TLV_FLAGS_DEVICE_PS_CMD,
IWM_UCODE_TLV_FLAGS_SCHED_SCAN,
IWM_UCODE_TLV_FLAGS_RX_ENERGY_API,
IWM_UCODE_TLV_FLAGS_TIME_EVENT_API_V2

* Also remove definitions and code for dealing with the v1 time-event api.

* Remove unneeded calc_rssi() function.

MFC r303322,303326,303327,303345,303413,303416,303418,303557

Update iwm(4) and iwmfw(4) to current in order to stabilize and improve
functionality.

Approved by: re (gjb)