pcnet32: fix non-napi packet reception

Recent changes to the driver for the new napi API broke the reception
of packets when in non-napi mode.  The initialization of napi.weight
was removed for the non-napi case leaving the value zero.

Tested NAPI and non-NAPI on x86_64.

Signed-off-by: Don Fry <pcnet32@verizon.net>
Signed-off-by: Jeff Garzik <jeff@garzik.org>