net: phy: mdio-moxart: remove unneeded include

mdio-moxart doesn't use regulators in the driver code. We can remove
the regulator include.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>