vfio: set errno on unsupported OS

vfio: set errno on unsupported OS

Currently, when code is running on FreeBSD or Windows, there is no way
to distinguish between a geniune error and a "VFIO is unsupported"
error. Fix the dummy implementations to also set the rte_errno flag.

Fixes: 279b581c897d ("vfio: expose functions")
Fixes: c564a2a20093 ("vfio: expose clear group function for internal usages")
Fixes: 964b2f3bfb07 ("vfio: export some internal functions")
Fixes: ea2dc1066870 ("vfio: add multi container support")
Cc: stable@dpdk.org
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Chenbo Xia <chenbo.xia@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>