mtd: rawnand: davinci: add ROM supported OOB layout

Add support for the OOB layout used by the ROM bootloader.
The same layout is used by both Keystone [1] and OMAPL138/DA850 [2]
which currently is the only users of davinci-nand.

Only select this layout if the `nand-is-boot-medium` property is set.
This to avoid breaking any existing devices out there.

[1] https://www.ti.com/lit/ug/spruhj3/spruhj3.pdf
[2] https://www.ti.com/lit/an/sprab41f/sprab41f.pdf



Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>