mali_kbase: platform: Add Pixel port for Mali GPU KMD

Sets up a simple platform port based off Arm's devicetree platform.

Created from platform/devicetree at SHA 395644cb0.

Bug: 156057140
Bug: 158091247
Signed-off-by: Sidath Senanayake <sidaths@google.com>
Change-Id: I4359363b24786b951a24acba23fe4d371f18c2bf