net: e1000: add defaults for i210 TX/RX PBSIZE

Set the defaults on probe for the packet buffer size registers
for the i210.

The TX/RX PBSIZE register of the i210 resets to its default value
only at power-on - see Intel Ethernet Controller I210 Datasheet rev 3.5
chapter 8.3 'Internal Packet Buffer Size Registers'.

If something (another driver, another OS, etc.) modifies this register
from its default value, the e1000 driver doesn't function correctly. It
detects a hang of the transmitter and continuously resets the adapter.
Here we set this value to its default when resetting the i210 to
resolve this issue.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>