ath6kl: add testmode 2 for 6003 ART

Add testmode 2 for 6003 ART. When you insmod ath6kl_sdio.ko testmode=2, ath6kl
will load ART firmware utf.bin and testscript nullTestFlow.bin. These files
should be put in the firmware folder.

kvalo: add "ath6kl:" to the title, word wrap the commit log and remove
extra line in the code

Signed-off-by: Alex Yang <xiaojuny@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>