net: phy: dp83848: Support ethernet pause frames

According to the documentation, the PHYs supported by this driver
can also support pause frames. Announce this to be so.
Tested with a TI83822I.

Acked-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>