drm/msm/dpu: add an API to reset the encoder related hw blocks

Add an API to reset the encoder related hw blocks to ensure
a proper teardown of the pipeline. At the moment this is being
used only for the writeback encoder but eventually we can start
using this for all interfaces.

changes in v4:
	- none

Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/483512/
Link: https://lore.kernel.org/r/1650984096-9964-10-git-send-email-quic_abhinavk@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>