Code which properly wants to handle Nand flash has to work
in a block based way since blocks are the entities that are erased or
may become bad. The regular mtd API works based on offsets in the device
which introduces unhandy 64bit arithmetics and the requirement to align
buffers to blocks.
This introduces the mtd peb API (PEB for physical Erase Block) which
allows the users to work in a block oriented way. The API is heavily
inspired by the UBI IO layer and in fact can replace parts thereof
later.

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