mwl8787: fix rftype params for 5ghz/ht40 channels

Now pass a chandef in so we can see the channel width
and secondary location.  We don't need to cache the current
channel; instead we can just look at the one in hw->conf.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
mwl8787: add a placeholder for sta_rc_update

I believe we'll need this or something like it to be able
to select rates properly.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
mwl8787: implement get_stats op

We ask the firmware for the values.  They seem reasonable;
e.g. setting RTS threshold then increases the RTS counters.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
mwl8787: small cleanup

Signed-off-by: Bob Copeland <me@bobcopeland.com>
mwl8787: clean up reset function

Fix a compiler warning about unused return result, as well as
cleanup spaces/tabs, reorder the error handling, and return
an error value instead of a boolean.

Signed-off-by: Bob Copeland <me@bobcopeland.com>