staging: wfx: drop useless function

staging: wfx: drop useless function

Since the code for multicast filtering has been dropped, the function
hif_set_data_filtering() is only called to disable multicast filtering.
In fact, the multicast filtering is already disabled by default. So,
this function is useless and can be dropped.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200907101521.66082-8-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>