Revert "net: phy: fixed_phy: Fix NULL vs IS_ERR() checking in __fixed_phy_register"

This reverts commit b45396afa4177f2b1ddfeff7185da733fade1dc3 ("net: phy:
fixed_phy: Fix NULL vs IS_ERR() checking in __fixed_phy_register")
since it prevents any system that uses a fixed PHY without a GPIO
descriptor from properly working:

[ 5.971952] brcm-systemport 9300000.ethernet: failed to register fixed PHY
[ 5.978854] brcm-systemport: probe of 9300000.ethernet failed with error -22
[ 5.986047] brcm-systemport 9400000.ethernet: failed to register fixed PHY
[ 5.992947] brcm-systemport: probe of 9400000.ethernet failed with error -22

Fixes: b45396afa417 ("net: phy: fixed_phy: Fix NULL vs IS_ERR() checking in __fixed_phy_register")
Signed-off-by: Florian Fainelli <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/phy/fixed_phy.c

···
 	/* Check if we have a GPIO associated with this fixed phy */
 	if (!gpiod) {
 		gpiod = fixed_phy_get_gpiod(np);
-		if (!gpiod)
-			return ERR_PTR(-EINVAL);
+		if (IS_ERR(gpiod))
+			return ERR_CAST(gpiod);
 	}
 
 	/* Get the next available PHY address, up to PHY_MAX_ADDR */