staging: unisys: Check return code properly on visor_copy_fragsinfo_from_skb

One call site for visor_copy_fragsinfo_from_skb was checking for an rc of
-1, but thhe function doesn't return that, it returns -errno.  Correct it

Signed-off-by: Neil Horman <nhorman@redhat.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>