Fix constness mixup in the declaration of writeChunkWithTagsToNAND.

In yaffs_guts.h the i4th arg of the writeChunkWithTagsToNAND method is
declared as "yaffs_ExtendedTags *" but in the correspondig implementation:
nandmtd2_WriteChunkWithTagsToNAND() & nandemul2k_WriteChunkWithTagsToNAND()
the same argument is declared as an const pointer of the same type.

Change the declaration of writeChunkWithTagsToNAND to also use the const.


-- Luc Van Oostenryck