msm: mdss: add sw_reset support for source pipes

In certain use-cases when under-run happens and simultaneously pipe is
un-staged from the mixer, pipe goes to bad state. In certain chip-sets,
sw_reset sequence is available to bring back pipe in a good state. Add
support for this sw_reset sequence.

Change-Id: I819a0ed4073d72571f3f663164a41823e947b71f
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>