staging: wfx: show counters of all interfaces

The device keep up to date three series of stats. One for each
virtual interface and one for the whole device.

Until to now, the stats for the whole device were unavailable. Moreover,
it is interesting to retrieve counters for all interfaces even if they
are not awake.

Change the counters available in debugfs in order to retrieve stats
from all interfaces.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200427134031.323403-13-Jerome.Pouiller@silabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>