drm/msm/mdp5: Create a separate MDP5 device

drm/msm/mdp5: Create a separate MDP5 device

In order to have a tree-like device hierarchy between MDSS and its
sub-blocks (MDP5, DSI, HDMI, eDP etc), we need to create a separate
device/driver for MDP5. Currently, MDP5 and MDSS are squashed
together are are tied to the top level platform_device, which is
also the one used to create drm_device.

The mdp5_kms_init code is split into two parts. The part where device
resources are allocated are associated with the MDP5 driver's probe,
the rest is executed later when we initialize modeset.

With this change, unlike MDP4, the MDP5 platform_device isn't tied to
the top level drm_device anymore. The top level drm_device is now
associated with a platform device that corresponds to MDSS wrapper
hardware.

Create mdp5_init/destroy funcs that will be used by the MDP5 driver
probe/remove. Use the HW_VERSION register in the MDP5 register address
space. Both the MDSS and MDP VERSION registers give out identical
version info.

The older mdp5_kms_init code is left as is for now, this would be removed
later when we have all the pieces to support the new device hierarchy.

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>