net/sfc/base: add function to create packed stream RxQ

net/sfc/base: add function to create packed stream RxQ

Encoding packed stream buffer size in RxQ type is not a future-proof
idea taking into account a new RxQ types with extra parameters.
To be consistent make packet stream buffer size a separate parameter.
In order to avoid blowing of the default RxQ create function prototype
add a dedicated function to create packed stream RxQ without not
applicable paramters.

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Andy Moreton <amoreton@solarflare.com>
Reviewed-by: Mark Spender <mspender@solarflare.com>