wil6210: reset buff id in status message after completion

Since DR bit and buffer id are written in different dwords of
the status message, the DR bit can already be set to 1 while the
buffer id is not updated yet.
Resetting the buffer id in the status message will allow the driver
to identify such cases and re-read the status message until the buffer
id is written by HW.
In case DR bit is set but buffer id is zero, need to read the status
message again, until a valid id is identified.

In addition to that, move the completed buffer id to the tail of the
free list to prevent its immediate reuse in the upcoming refill.

Change-Id: Ibdbaa1542940b975cd7669fb30548998222b359e
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Lior David <liord@codeaurora.org>