nand_util: convert nand_write_skip_bad() to flags

In a future commit the behaviour of nand_write_skip_bad()
will be further extended.

Convert the only flag currently passed to the nand_write_
skip_bad() function to a bitfield of only one allocated
member. This should avoid an explosion of int's at the
end of the parameter list or the ambiguous calls like

nand_write_skip_bad(info, offset, len, buf, 0, 1, 1);
nand_write_skip_bad(info, offset, len, buf, 0, 1, 0);

Instead there will be:

nand_write_skip_bad(info, offset, len, buf, WITH_YAFFS_OOB |
			WITH_OTHER);

Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Acked-by: Detlev Zundel <dzu@denx.de>
Signed-off-by: Scott Wood <scottwood@freescale.com>