drm/msm/dsi-staging: update dma watermarks with recommended values.

Disable the read and water watermarks for cmd dma in embedded mode
so that dsi fetches full command before starting kickoff.
And also update recommended watermark values for 
commands in non-embedded mode.

Change-Id: Ib04fdab7f71ded439baeb2d6728ddb36e2f32bc8
Signed-off-by: Vara Reddy <varar@codeaurora.org>