dmaengine: qcom: bam_dma: document controlled-remotely dt property

Extend BAM dt bindings with controlled-remotely property. The
property will be needed to handle cases where we need to skip
register writes to initialise BAM hardware block.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Reviewed-by: Andy Gross <andy.gross@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>