[Yaffs] 2.4.25-vrs2-tcl1 update

I added a fix to kernel 2.4.25-vrs2-tcl1.
The problem was that in nand_scan oobavail was calculated according to
the bus width not page size ie 2 bytes on a 16 bit bus. I patched in the
alternative calculation method used in 2.6.16.5

The yaffs2 port is only affected in so much that it now doesn't segfault
with this kernel.

Nick