r8169: use fsleep in polling functions

Use new flexible sleep function fsleep() to merge the udelay and msleep
polling functions. We can safely do this because no polling function
is used in atomic context in this driver.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>