ieee1275: encode-unit command for 4 addr cell devs

ieee1275: encode-unit command for 4 addr cell devs

Convert physical address to text unit-string.

Convert phys.lo ... phys-high, the numerical representation, to unit-string,
the text string 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>