wil6210: free edma_rx_swtail upon reset

edma_rx_swtail dma memory free is missing.
Add this part of Rx desc ring free.

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