tg3: Convert ISR parameter to tnapi

This patch migrates the ISR parameter from struct net_device to struct
tg3_napi.  Checkpatch complains about the existence of the preexisting
IRQF_SAMPLE_RANDOM flag.  I've opted to keep this patch conservative and
let it continue to exist until the flag gets officially purged from the
kernel.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>