venus: properly support GPU_DATA_BUFFER for AHB

CrOS gralloc was missing support for GPU_DATA_BUFFER, which was only fixed until recently(https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2974800). Now we can allcate properly.

This patch also removes a redundant TODO regarding image format list support for AHB. vkGetPhysicalDeviceImageFormatProperties2 has already checked the support for such though it only checks whether the optimal tiling and the associated drm format modifier for the AHB image format itself applies to the entire format list or not. Given the use case for such combination is quite limited, we choose not to add new gralloc support to force linear modifier as a fallback for wider coverage.

/cc @olv