Extend the block i/o system to allow registered devices to advertise
an erase geometry. Devices which do not need to be explicitly erased
may skip this. Extent the Zynq spiflash code to publish the erase
geometry as read from the flash device.
Signed-off-by: John Grossman <johngro@google.com>
Change-Id: I42e16fbe9a0fcf8334c317f16dea1c551c203eb2