[magma] Switch to magma_map_buffer

Bug:105580

Change-Id: I9db569a5c9001ee013c544f65958223efa21c354
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/github.com/intel/media-driver/+/714182
Reviewed-by: John Bauman <jbauman@google.com>
1 file changed