arm64: dts: hikey: Add DMA entries for Bluetooth UART

arm64: dts: hikey: Add DMA entries for Bluetooth UART

Add dma0 references for bluetooth uart to enable dma
for bt transfers.

Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Ryan Grachek <ryan@edited.us>
Cc: Wei Xu <xuwei5@hisilicon.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: devicetree@vger.kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>