Some external device memories really represent existing images
with requirements and not just memory blobs. For AHB, retrieve
planes offsets and row strides from the gralloc plane metadata.

Bug: b/171302758
Test: launch Cuttlefish w/ SwANGLE and open camera
Change-Id: I9af7aae9d19035cacd736b127b9d03cee4374fab
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/51048
Presubmit-Ready: Jason Macnak <natsu@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Jason Macnak <natsu@google.com>
Commit-Queue: Jason Macnak <natsu@google.com>