commit d319fe2a upstream.

We don't expect to get errors from the hypervisor when reading the rng,
but if we do we should pass the error up to the hwrng driver. Otherwise
the hwrng driver will continue calling us forever.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>