disp: msm: clear dma done interrupt status for slave controller

When Broadcast is enabled, DMA_DONE bit gets set for slave
controller on command transfer completion but it is not
getting cleared. Due to this, DMA transfer failures on slave
controller are not getting caught. This patch add supports for
clearing DMA_DONE for slave controller on every successful
transfer. This also prints error if transfer fails on slave
controller.

Change-Id: I61ce7b2d8be323adc70d888b5a2416afd9ae9fac
Signed-off-by: Harigovindan P <harigovi@codeaurora.org>