mtd: onenand: Add support for 8Gb datasize onenand

Used in several S5PV210-based Galaxy S devices, among them SGH-T959V,
SGH-T959P, SGH-T839, and SPH-D700.

Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>