wil6210: prevent usage of tx ring 0 for eDMA

In enhanced DMA ring 0 is used for RX ring, hence TX ring 0
is an unused element in ring_tx and ring2cid_tid arrays.
Initialize ring2cid_tid CID to WIL6210_MAX_CID to prevent a false
match of CID 0.
Go over the ring_tx and ring2cid_tid from wil_get_min_tx_ring_id
and on to prevent access to index 0 in eDMA.

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