net: phy: allow for reset line to be tied to a sleepy GPIO controller

mdio_device_reset() makes use of the atomic-pretending API flavor for
handling the PHY reset GPIO line.

I found no hint that mdio_device_reset() is called from atomic context
and indeed it uses usleep_range() since long time, so I would assume that
it is OK to sleep there.

This patch switch to gpiod_set_value_cansleep() in mdio_device_reset().
This is relevant if e.g. the PHY reset line is tied to a I2C GPIO
controller.

This has been tested on a ZynqMP board running an upstream 4.19 kernel and
then hand-ported on current kernel tree.

Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>