staging: wfx: fix typo in "num_of_ssi_ds"

The script that has imported API headers has made a mistake in
"num_of_ssi_ds".

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20191217161318.31402-24-Jerome.Pouiller@silabs.com


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