Don't allow to trigger SBR from a VF running in VMM context.

Cc: stable@vger.kernel.org
Signed-off-by: Conor McLoughlin <conor.mcloughlin@intel.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>