ath6kl: Increase the maximum number of connections in AP mode

The maximum number of clients which ath6kl can support in AP mode
is 10. The limitation of 8 connections is only for older chipsets
which ath6kl does not support.

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