wil6210: fix eDMA RX chaining

HW requires Rx buffers to be 4 bytes aligned. Modify the driver to
meet this requirement.
Enable OFU rdy valid bug fix, to prevent hang in oful34_rx while
there is back-pressure from host during RX.

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