drm/msm/sde: remove static allocation of mdp_top hw block

Remove singleton behavior from mdp_top hardware block since it
is no longer necessary. The resource manager now manages the
lifecycle of the mdp_top. This fixes an issue where the static
mdp_top would point to freed memory.

Change-Id: Ie860fd65ac2efa28ed0f3d9014bb45b0cc6aed5e
Signed-off-by: Lloyd Atkinson <latkinso@codeaurora.org>