disp: msm: sde: remove all preclose logic

The DRM framework only calls the driver's preclose callback
function if the LEGACY driver feature is enabled. Therefore
strip out this logic as it never gets executed since LEGACY
is not supported for msm_drm driver.

Change-Id: I95474cd5424423ef194faae12f1241698f3e467e
Signed-off-by: Steve Cohen <cohens@codeaurora.org>