ieee1275: decode-unit command for 4 addr cell devs

ieee1275: decode-unit command for 4 addr cell devs

decode-unit ( addr len -- phys.lo ... phys.hi )

Convert text unit-string to physical address.

Convert unit-string, the text string representation, to phys.lo ... phys.hi,
the numerical representation of a physical address within the address space
defined by this device node. The number of cells in the list
phys.lo ... phys.hi is determined by the value of the #address-cells
property of this node.

This function is for devices with #address-cells == 4

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>