drm/msm: disable mdp4 driver in drm kms

mdp4 drm driver is for old MDP revision. It
is not required for newer version of chipsets.
Disable this driver because it is using older
smmu/bus APIs which are not supported now.

Conflicts:
	drivers/gpu/drm/msm/Kconfig

Change-Id: Ic25e77112a378b96295d78f1bd9d8f48a07be32d
Signed-off-by: Stephane Viau <sviau@codeaurora.org>
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>
[narendram@codeaurora.org: resolve Kconfig merge conflict]
Signed-off-by: Narendra Muppalla <narendram@codeaurora.org>