wil6210: support Talyn specific board file

FW file name for Talyn device can be different from the default name.
In such a case use a corresponding board file name.
If such a board file is not present FW download procedure will fail.

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