Some Overo COM models include NAND flash in the on-board
package-on-package (PoP) chip. Add this to the base Overo devicetree.
Most commonly, this is 512MB NAND from the Micron MT29C4G96MAZ family
but, as discussed [1], several different sized are possible. To
support different sizes, the last partition should fill to the end of
the chip (i.e. MTDPART_SIZ_FULL).
With thanks to Florian Vaussard for the original patch [2] and Adam Lee for
updating it here.