Fix SED-OPAL UAPI structs to prevent 32/64 bit size differences.

This patch is a quick fixup of the user structures that will prevent
the structures from being different sizes on 32 and 64 bit archs.
Taking this fix will allow us to *NOT* have to do compat ioctls for
the sed code.

Signed-off-by: Scott Bauer <scott.bauer@intel.com>
Fixes: 19641f2d ("Include: Uapi: Add user ABI for Sed/Opal")
Signed-off-by: Jens Axboe <axboe@fb.com>