Instead, explicitly add padding field, and adjust member ordering to
eliminate compiler-added padding between members, and at the end of the
struct (if possible: some structs end in a u8[0] array.)
This should prevent unaligned accesses. Not a big deal on x86_64, but
other archs like aarch64 really want this.
Signed-off-by: Andy Grover <agrover@versity.com>