MTD: mtdconcat NAND/Sibley support (rev.2)

There is a second revision of "mtdconcat NAND/Sibley" patch. I hope
the patch will not get damaged as I'm posting it from gmail account,
thanks to Jorn.

The patch adds previously missing concat_writev(),
concat_writev_ecc(), concat_block_isbad(), concat_block_markbad()
functions to make concatenation layer compatible with Sibley and NAND
chips.

Patch has been cleared from whitespaces, fixed some lines of code as
requested. Also I have added code for alignment check that should
support Jorn's "writesize" patch.

Signed-off-by: Alexander Belyakov <alexander.belyakov@intel.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>