block: Implement DiskFile marker trait for RawFileDiskAio

Add empty disk_file::DiskFile impl for RawFileDiskAio.
This marker supertrait requires DiskSize + Geometry + Sync,
all of which are now satisfied.

Signed-off-by: Muminul Islam <muislam@microsoft.com>

block/src/raw_async_aio.rs

@@ -115,6 +115,8 @@ impl disk_file::Resizable for RawFileDiskAio {
     }
 }
 
+impl disk_file::DiskFile for RawFileDiskAio {}
+
 pub struct RawFileAsyncAio {
     fd: RawFd,
     ctx: aio::IoContext,