drm/msm/sde: Add check before applying color-prop properties

After device goes into suspend state for a while, we notice that
atomic commit calls are made, and they will cause all the dirty
color-processing properties to be applied during suspend state.
When device actually resumes, all the dirty color-processing
won't be applied again and cause color-processing features not
persist over suspend/resume.
This change adds a check to make sure sde_crtc is enabled before
applying color-processing properties to avoid the issue.

Change-Id: I62acfd65bac4ce93eb82a6cede4df9d12746b22e
Signed-off-by: Ping Li <pingli@codeaurora.org>