p54: disable channels with incomplete calibration data sets

James Grossmann [1] reported that p54 spews out confusing
messages instead of preventing the mayhem from happening.

the reason is that "p54: generate channel list dynamically"
is not perfect. It didn't discard incomplete channel data
sets and therefore p54 advertised to support them as well.

[1]: http://marc.info/?l=linux-wireless&m=125699830215890



Cc: Larry Finger <Larry.Finger@lwfinger.net>
Reported-by: James Grossmann <cctsurf@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>