tg3: remove IRQF_SAMPLE_RANDOM flag

This driver is the last user of the IRQF_SAMPLE_RANDOM flag for net drivers, and since add_*_randomness
interfaces have now deprecated the flag as a source of external noise, we can remove it.

Signed-off-by: Davidlohr Bueso <dave@gnu.org>
Signed-off-by: David S. Miller <davem@davemloft.net>