wil6210: initialize TX and RX enhanced DMA rings

wil6210: initialize TX and RX enhanced DMA rings

Enhanced DMA design includes the following rings:
- Single RX descriptor ring is used for all VIFs
- Multiple RX status rings are supported, to allow RSS
- TX descriptor ring is allocated per connection
- A single TX status ring is used for all TX descriptor rings

This patch initializes and frees the above descriptor and
status rings.

The RX SKBs are handled by a new entity of RX buffers manager,
which handles RX buffers, each one points to an allocated SKB.
During Rx completion processing, the driver extracts a buffer
ID which is used as an index to the buffers array.
After the SKB is freed the buffer is moved from the 'active'
list to the 'free' list, indicating it can be used for another
descriptor. During Rx refill, SKBs are allocated and attached
to 'free' buffers. Those buffers are attached to new descriptors
and moved to the 'active' list.

New debugfs entries were added to allow edma configuration:

Run the following command to configure the number of status rings:
echo NUM_OF_STATUS_RINGS > num_rx_status_rings

Run the following command to use extended RX status message for
additional debug fields from HW:
echo 0 > compressed_rx_status

Run the following command to control the size of the TX status ring:
echo TX_STATUS_RING_ORDER > tx_status_ring_order
The status ring size will be 1 << tx_status_ring_order

Run the following command to control the size of the RX status ring:
echo RX_STATUS_RING_ORDER > rx_status_ring_order
Due to HW constrains RX sring order should be bigger than RX ring order
The status ring size will be 1 << rx_status_ring_order

Run the following command to change the number of RX buffer IDs:
echo RX_BUFF_ID_COUNT > rx_buff_id_count

Signed-off-by: Gidon Studinski <gidons@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>