Fix potential small memory leak

In __reg_val() in case the 'if (per_port && tdport)' condition is
true, we leak the previously allocated char *subpath.
Instead jump to 'errorout' which frees it, just like the other error
paths do in this function.

Signed-off-by: Michele Baldessari <michele@acksyn.org>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>