mtd: nand: update nand_default_block_markbad()

This is an update that depends on the previous patches I sent.

We can now write to all the appropriate BB marker locations (i.e.
pages 1 AND 2, bytes 1 AND 6) with nand_default_block_markbad() if
necessary, according to the flags marked in chip->options.

Note that I removed the line:
	ofs += mtd->oobsize;
Unless I am wrong, this line was completely unnecessary in the
first place.

Signed-off-by: Brian Norris <norris@broadcom.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>