ath6kl: Fix target assert in p2p bringup with multi vif

Using interface 0 for p2p causes target assert. This is because
interface 0 is always initialized to non-p2p operations. Fix this
issue by initializing all the interfaces for p2p when fw is capable
of dynamic interface switching. When fw is not capable of dynamic
switching, make sure p2p is not brought up on interface which is
not initialized for this purpose.

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