This removes the dependency on GPIOLIB for non faulty PHYs.

Indeed, without this patch, if GPIOLIB is not selected
devm_gpiod_get_optional() will return -ENOSYS and the driver probe
call will fail, regardless of the actual PHY hardware.

Out of the 3 PHYs supported by this driver (AT8030, AT8031, AT8035),
only AT8030 presents the issues that commit 13a56b44 ("net: phy:
at803x: Add support for hardware reset") attempts to work-around by
using a 'reset' GPIO line.

Hence, only AT8030 should depend on GPIOLIB operating properly.

Fixes: 13a56b44 ("net: phy: at803x: Add support for hardware reset")
Signed-off-by: Sebastian Frias <sf84@laposte.net>
Signed-off-by: David S. Miller <davem@davemloft.net>