Bluetooth: btusb: Add CONFIG_BT_HCIBTUSB_POLL_SYNC

This adds CONFIG_BT_HCIBTUSB_POLL_SYNC which can be used to set the
default behavior of Bluetooth USB controller with respect to poll
synchronization of its endpoits.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Tested-by: Tedd Ho-Jeong An <tedd.an@intel.com>