staging: wfx: explain the purpose of wfx_send_pds()

On first look, the goal of wfx_send_pds() is not obvious. A small
explanation is welcomed.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20210913130203.1903622-31-Jerome.Pouiller@silabs.com


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