Doing a device information query on a non-PCI device such as
vhost was resulting in the dereferencing of a NULL pointer
(the absent PCI data), causing a segmentation fault.
Fixes: bda68ab9d1e7 ("examples/ethtool: add user-space ethtool sample application")
Signed-off-by: Remy Horton <remy.horton@intel.com>