staging: wfx: fix misleading 'rate_id' usage

The driver sometime use the term 'rate_id' to identify a retry policy
(which is in fact a series of rate IDs). This is misleading.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20210913130203.1903622-16-Jerome.Pouiller@silabs.com


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