net: hns: mdio->irq is an array, so no need to check if it is null

The null check on mdio->irq is redundant since mdio->irq is an array
of PHY_MAX_ADDR ints and hence can never be null. Remove the redundant
check.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>