block/vhdx: Use IEC binary prefixes for size constants

block/vhdx: Use IEC binary prefixes for size constants

Using IEC binary prefixes in order to make the code more readable,
with the exception of DEFAULT_LOG_SIZE because it's passed to
stringify().

Signed-off-by: Stefano Garzarella <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: John Snow <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>