mtd: nand: mxc: Fix mxc_v1 ooblayout

Commit a894cf6c ("mtd: nand: mxc: switch to mtd_ooblayout_ops")
introduced a bug in the OOB layout description. Even if the driver claims
that 3 ECC bytes are reserved to protect 512 bytes of data, it's actually
5 ECC bytes to protect 512+6 bytes of data (some OOB bytes are also
protected using extra ECC bytes).

Fix the mxc_v1_ooblayout_{free,ecc}() functions to reflect this behavior.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Fixes: a894cf6c ("mtd: nand: mxc: switch to mtd_ooblayout_ops")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>