dm9000: Add regulator and reset support to dm9000

In boards, the dm9000 chip's power and reset can be controlled by gpio.

It makes sense to add them to the dm9000 driver and let dt be used to
enable power and reset the phy.

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: David S. Miller <davem@davemloft.net>