Under certain configuration SEV functions can be defined as no-op.
In such a case error can be uninitialized.

Initialize the variable to 0.

Cc: Dan Carpenter <Dan.Carpenter@oracle.com>
Reported-by: Dan Carpenter <Dan.Carpenter@oracle.com>
Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
Acked-by: Gary R Hook <gary.hook@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>