net: phy: fix phy_get_internal_delay accessing an empty array

The phy_get_internal_delay function could try to access to an empty
array in the case that the driver is calling phy_get_internal_delay
without defining delay_values and rx-internal-delay-ps or
tx-internal-delay-ps is defined to 0 in the device-tree.
This will lead to "unable to handle kernel NULL pointer dereference at
virtual address 0". To avoid this kernel oops, the test should be delay
>= 0. As there is already delay < 0 test just before, the test could
only be size == 0.

Fixes: 92252ee ("net: phy: Add a helper to return the index for of the internal delay")
Co-developed-by: Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@savoirfairelinux.com>
Signed-off-by: Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@savoirfairelinux.com>
Signed-off-by: Kévin L'hôpital <kevin.lhopital@savoirfairelinux.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: kevlhop

drivers/net/phy/phy_device.c

@@ -2959,7 +2959,7 @@ s32 phy_get_internal_delay(struct phy_device *phydev, struct device *dev,
 	if (delay < 0)
 		return delay;
 
-	if (delay && size == 0)
+	if (size == 0)
 		return delay;
 
 	if (delay < delay_values[0] || delay > delay_values[size - 1]) {