tg3: Revert PCIe tx glitch fix

This patch reverts commit 52cdf852,
entitled "tg3: Prevent a PCIe tx glitch".  The problem does not have
any visible side-effects and happens too early for the driver to do
anything about it.  The proper place for this code is within the
device's bootcode.

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