natsemi: fix netdev error acounting

When a detailed netdev error is counted, we also must account for it in the
aggregated error count.

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=8106



Cc: Tim Hockin <thockin@hockin.org>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Chongfeng Hu <loveminix@yahoo.com.cn>
Cc: Natalie Protasevich <protasnb@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>