[MTD] [NAND] nand_base.c: fix type of eccpos pointer

The nand_base.c driver implicitly casts the uint32_t
eccpos array to 'int *', which is not only not guaranteed
to be the same sign as the source, but is not guaranteed
to be the same size.

Fix by changing nand_base.c to use uint32_t
referencing the eccpos fields.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>