staging: wfx: send rate policies one by one

staging: wfx: send rate policies one by one

Rate policies (aka. tx_rate_retry_policy in hardware API) are sent to
device asynchronously from tx requests. So, the device maintains a list
of active rate policies and the tx requests only reference an existent
rate policy.

The device API allows to send multiple rate policies at once. However,
this property is very rarely used. We prefer to send rate policies one
by one and simplify the architecture.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200115135338.14374-5-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>