Revert openwrt patch which caused too high tx powers

Since the reverted patch, device specific antenna gain is not set for some reason.
Reverting the patch in question fixes this issue.

THIS SHOULD BE ONLY CONSIDERD AS A TEMPORARY FIX UNTIL THE ISSUE IS FIXED PROPERLY!

Fixes: #85

Signed-off-by: Fabian Bläse <fabian@blaese.de>
Tested-by: Fabian Bläse <fabian@blaese.de>
Tested-by: Christian Dresel <fff@chrisi01.de>
Reviewed-by: Tim Niemeyer <tim@tn-x.org>