staging: wfx: drop useless union hif_indication_data

staging: wfx: drop useless union hif_indication_data

The union hif_indication_data is never used in the driver. So, it is not
necessary to declare it separately from hif_ind_generic.

In add, drop prefix 'indication_' from the names 'indication_type' and
'indication_data' since it is redundant with the name of the struct.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200907101521.66082-25-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>