ath6kl: print firmware capabilities

Printin the  firmware capabilities during the first firmware boot makes it easier to find out what
features firmware supports.

Obligatory screenshot:

[21025.678481] ath6kl: ar6003 hw 2.1.1 sdio fw 3.2.0.144 api 3
[21025.678667] ath6kl: firmware supports: sched-scan,sta-p2pdev-duplex,rsn-cap-override

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