drm/msm/sde: setup blend function for sdm855

This change adds the sdm855 chipset to this list of
chipsets which can use the implementation of blending function.

Change-Id: I029de7a2c65c9d7446b18309c9c7be7535375e91
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>