of_mdio: kill useless variable in of_mdiobus_register()

of_mdiobus_register()  declares the 'paddr' variable to hold the result of
the of_get_property()  but only uses it once after that while the function
can be called directly from the *if* statement. Remove that variable and
switch to calling of_find_property() instead since  we don't care about
the "reg" property's value anyway...

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