of: Allow busses with #size-cells=0

of: Allow busses with #size-cells=0

It's quite legitimate for a DT node to specify #size-cells=0. One example
is a node that's used to collect a number of non-memory-mapped devices.
In that scenario, there may be multiple child nodes with the same name
(type) thus necessitating the use of unit addresses in node names, and
reg properties:

/ {
	regulators {
		compatible = "simple-bus";
		#address-cells = <1>;
		#size-cells = <0>;

		regulator@0 {
			compatible = "regulator-fixed";
			reg = <0>;
			...
		};

		regulator@1 {
			compatible = "regulator-fixed";
			reg = <1>;
			...
		};

		...
	};
};

However, #size-cells=0 prevents translation of reg property values into
the parent node's address space. In turn, this triggers the kernel to
emit error messages during boot, such as:

    prom_parse: Bad cell count for /regulators/regulator@0

To prevent printing these error messages for legitimate DT content, a
number of changes are made:

1) of_get_address()/of_get_pci_address() are modified only to validate
   the value of #address-cells, and not #size-cells.

2) of_can_translate_address() is added to indicate whether address
   translation is possible.

3) of_device_make_bus_id() is modified to name devices based on the
   translated address only where possible, and otherwise fall back to
   using the (first cell of the) raw untranslated address.

4) of_device_alloc() is modified to create memory resources for a device
   only if the address can be translated into the CPU's address space.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>