dmaengine: qcom_bam_dma: Add device tree binding

Add device tree binding support for the QCOM BAM DMA driver.

Acked-by: Kumar Gala <galak@codeaurora.org>
Signed-off-by: Andy Gross <agross@codeaurora.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>