staging: wfx: simplify hif_handle_tx_data()

Since enum action has now only two cases, it can be dropped. Then
hif_handle_tx_data() can be simplified.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200115135338.14374-63-Jerome.Pouiller@silabs.com


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