cnss2: Add prefix to firmware name based on device ID

WLAN firmware files will be stored at different places based on
different device IDs. Hence add prefix to firmware name in order
to load firmware files correctly.

Change-Id: I6c92f2384fa81917ebfb01b80d8a2ee6c2c756b6
Signed-off-by: Yue Ma <yuem@codeaurora.org>