MAINTAINERS: add ath10k

I forgot to add an entry to MAINTAINERS when submitting the driver.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
MAINTAINERS: update ath6kl git location

The git tree is in github.com nowadays.

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