[TG3]: Fix link problem on Dell's onboard 5906.

The bug is caused by code that always set
(TG3_FLAG_USE_MI_INTERRUPT | TG3_FLAG_USE_LINKCHG_REG) on all Dell's
onboard devices.  With these 2 flags set, the link status is polled
by tg3_timer() and will only work when the PHY is set up to interrupt
the MAC on link changes.  This breaks 5906 because the 5906 PHY does
not support TG3_FLAG_USE_MI_INTERRUPT the same as other PHYs.

For correctness, only Dell's onboard 5701 needs these 2 flags to be
set.  This change will fix the 5906 problem and will change other
Dell devices except 5700 and 5701 to use the more efficient
interrupt-driven link changes.

Update version to 3.77.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>