dfu_free_entities() invoking dfu_free_entity_sf() has let to segementation
faults due to double freeing the same device.
spi_flash_free() is not relevant for the driver model but exists only for
compatibility with old drivers.
We must not remove any device here:
* The device may still be referenced.
* We don't want to have to probe again.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
b09c74f66d