gralloc: Let gralloc_priv.h be overloaded by device trees

Adjustments to private_handle_t may be necessary for device-specific
blob compatibility, so don't enforce usage of the local header

Change-Id: I588ca59ed76b1a063a4b663ac2c98589865b7738
display: Add support for MDP 4.1

 * MDP 4.1 does not support the borderfill pipe and the baselayer logic
   should not be used.
 * Only use 3 pipes for MDP 4.1.

Change-Id: Ide542079902f35818300619f8eefd3d188342b5d
display: Fix support for MDP 4.1

 * MDP 4.1 still does not support the borderfill pipe, baselayer logic
   should not be used.

Change-Id: I587bdff4a03ced141e43819eea70cec1aedaeb7b