staging: wfx: firmware does not support more than 32 total retries

The sum of all retries for a Tx frame cannot be superior to 32.

There are 4 rates at most. So this patch limits number of retries per
rate to 8.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20191217161318.31402-6-Jerome.Pouiller@silabs.com


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