drivers: ethernet: vsc8541: Fixed inverted reset GPIO

For GPIOs driving active-low signals, such as the VSC8541's reset pin,
they are supposed to be declared as active low in the device tree, and
set to 1 to assert and 0 to clear. Change the driver as such so that it
does not leave the PHY stuck in reset when so configured.

Also changed all in-tree board DTS files for this PHY to properly
declare the reset GPIO as active low.

Signed-off-by: Robert Hancock <robert.hancock@calian.com>