ss: Fix return value checks for net_*_open

In ss.c, generic_proc_open(), for which the net_*_open functions are just
convenient wrappers, uses fopen, so errors are signalled by a NULL return
value. Some checks were expecting negative values instead, fix them.

Signed-off-by: Björn Steinbrink <B.Steinbrink@gmx.de>
Signed-off-by: Stephen Hemminger <stephen.hemminger@vyatta.com>
1 file changed