of_mdio: kill useless variable in of_phy_register_fixed_link()

of_phy_register_fixed_link() declares the 'err' variable to hold the result
of of_property_read_string() but only uses it once after that, while that
function can be called directly from the *if* statement...

Remove that variable and move/regroup 'link_gpio' and 'len' variables in
order to sort the declarations in the reverse Xmas tree order -- to please
DaveM. ;-)

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>