gve: Remove qpl_cfg struct since qpl_ids map with queues respectively

The qpl_cfg struct was used to make sure that no two different queues
are using QPL with the same qpl_id. We can remove that qpl_cfg struct
since now the qpl_ids map with the queues respectively as follows:
For tx queues: qpl_id = tx_qid
For rx queues: qpl_id = max_tx_queues + rx_qid

And when XDP is used, it will need the user to reduce the tx queues to
be at most half of the max_tx_queues. Then it will use the same number
of tx queues starting from the end of existing tx queues for XDP. So the
XDP queues will not exceed the max_tx_queues range and will not overlap
with the rx queues, where the qpl_ids will not have overlapping too.

Considering of that, we remove the qpl_cfg struct to get the qpl_id
directly based on the queue id. Unless we are erroneously allocating a
rx/tx queue that has already been allocated, we would never allocate
the qpl with the same qpl_id twice. In that case, it should fail much
earlier than the QPL assignment.

Suggested-by: Praveen Kaligineedi <pkaligineedi@google.com>
Signed-off-by: Ziwei Xiao <ziweixiao@google.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Reviewed-by: Shailend Chand <shailend@google.com>
Link: https://lore.kernel.org/r/20240417205757.778551-1-ziweixiao@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>