sky2: Threshold for Pause Packet is set wrong

The sky2 driver sets the Rx Upper Threshold for Pause Packet generation to a
wrong value which leads to only 2kB of RAM remaining space. This can lead to
Rx overflow errors even with activated flow-control.

Fix: We should increase the value to 8192/8

Signed-off-by: Mirko Lindner <mlindner@marvell.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>