Enable blsp1_uart3, define its pinconf and add the bluetooth node.

It seems provisioning is lacking a valid BD address, preventing the
interface from initializing, so provide a dummy for now.
Tested-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>