dt-bindings: dma: qcom,bam-dma: Add 'interconnects' and 'interconnect-names'

Add 'interconnects' and 'interconnect-names' as optional properties
to the device-tree binding documentation for BAM DMA IP.

These properties describe the interconnect path between BAM and main
memory and the interconnect type respectively.

Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>