If a device does not have bad blocks loop over the eraseblocks
in the driver instead of the core. This allows the mtd_dataflash
driver to erase blocks instead of pages to gain more speed during
erasing. Also the mtd_dataflash driver modifies the erase_info
struct which causes the outer loop in the core to never end.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>