openrisc: remove the redundant of_platform_populate

The of_platform_populate call in the openrisc arch code is now redundant
as the DT core provides a default call. Openrisc has a NULL match table
which means only top level nodes with compatible strings will have
devices creates. The default version will also descend nodes in the
match table such as "simple-bus" which should be fine as openrisc
doesn't have any of these (though it is preferred that memory-mapped
peripherals be grouped under a bus node(s)).

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Jonas Bonn <jonas@southpole.se>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Stafford Horne <shorne@gmail.com>