The count argument to ipa_endpoint_replenish() is only ever 0 or 1,
and always will be (because we always handle each receive buffer in
a single transaction).  Rename the argument to be add_one and change
it to be Boolean.

Update the function description to reflect the current code.
Signed-off-by: NAlex Elder <elder@linaro.org>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>