gatt: Fix reconnection on Bluetooth On.

When Bluetooth is turning On, Android tries to connect to any of the
known devices using direct connect allocating transport control blocks
(tcb). If there is more than 7 (GATT_MAX_PHY_CHANNEL) LE devices on the list,
only first 7 devices will be doing direct connect. Other devices will not be
connected unless user (usually gatt client application) does background connect.

However, if device from the background connect gets connected (ACL will
be created) during first 30 sec after BT is ON, the device will not be
connected to GATT as all tcbs are still in use for direct connect.

With this patch, TCB block is allocated when ACLs is established.

Bug: 325438660
Bug: 325595120
Test: mmm packages/modules/Bluetooth
Test: reconnect multiple devices on Bluetooth On
Test: multiple configuration tests e.g. having GATT_MAX_PHY_CHANNEL=1

Change-Id: I3cca7301c9e6d42fc6c9095215ecde1aec6d0b33