They are (unlike rest of sd8xxx images from libertas/ and mrvl/) not Libertas
WiFi specific and are used for the bluetooth controller (btmrvl) which does not
look for them in libertas/.

Provide a compatibility symbolic link to avoid breaking libertas_sdio drivers
that are already in use.
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>