fabrics: print an error for ENOENT too

fabrics: print an error for ENOENT too

Many nvme commands such as discover, connect, connect-all, etc.
simply return to the prompt without printing any useful error
message when the respective nvme driver modules are not loaded in
the kernel. This is because nothing gets printed when
nvme_scan_topology() returns an ENOENT due to missing nvme system
files stemming from not loading the appropriate nvme modules.
Fix the same.

Signed-off-by: Martin George <marting@netapp.com>