ibacm: use sysfs (in acm_if_is_ib) rather than ioctl(... SIOCGIFHWADDR ...) to read...

ibacm: use sysfs (in acm_if_is_ib) rather than ioctl(... SIOCGIFHWADDR ...) to read interface type

Getting an interface type from sysfs is easier than using an ioctl when an
interface name is readily available (as is the case with netlink.)

In preparation for netlink support create a function which uses sysfs and use
it instead of ioctls.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Sean Hefty <sean.hefty@intel.com>