Bluetooth: Set A2MP response timeout to 8 seconds

The A2MP response timeout should be greater than the Connection
Accept timeout set for AMP links, but less than the Link Supervision
Timeout on the BR-EDR link.

This allows for A2MP to fail, but the ACL connection can remain
established, so transfer can continue on BR-EDR.

Change-Id: I654ed12149d9cf194c07b1eb3433e8c23720a209
Signed-off-by: Peter Krystad <pkrystad@codeaurora.org>