laptop-mode-tools: switch wifi support to be nl80211-only

laptop-mode-tools: switch wifi support to be nl80211-only

We support only nl80211 WiFi devices; no more WEXT support:
- remove old script that used iwconfig
- add new module script that uses iw to ena/dis power save

Note this also fixes wifi power save operation for nl80211 devices as the iwconfig code never worked right due to it checking the wrong file under /sys.  This means we should now have lower latency on AC because we'll turn off power save.

BUG=7138
TEST=gmerge to device; suspend+resume and check power save state of wlan0; also run sh -x laptop_mode auto force and verify the right things are happenig for wifi devices

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=c486fbc

[Sam Leffler, 2010-11-10 00:37:30]

Hope you weren't actively working on this; just noticed it while working on
related stuff.

There is a companion CL w/ an ebuild change.

[Sameer Nanda, 2010-11-10 17:48:38]

LGTM. Feel free to delete wifi-powermgt module.  It was added by us and doesn't
exist upstream.  Now that we're moving away from iwconfig, it won't serve any
useful purpose.

[Sam Leffler, 2010-11-10 18:22:21]

Removed iwconfig-based support and fixed issue before push.  Thank you!