wil6210: free edma_rx_swtail upon reset

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

Change-Id: I6ad40cab87898d0a9af977f648b47a4a3cda3a8c
Signed-off-by: Dedy Lansky <dlansky@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Git-commit: 29ca376066df05760a7d7038a95aba1c3b968e9e
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git


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