mtd: rawnand: sunxi: Write pageprog related opcodes to WCMD_SET

The opcodes used by the controller when doing batched page prog should
be written in NFC_REG_WCMD_SET not FC_REG_RCMD_SET. Luckily, the
default NFC_REG_WCMD_SET value matches the one we set in the driver
which explains why we didn't notice the problem.

Fixes: 614049a8 ("mtd: nand: sunxi: add support for DMA assisted operations")
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>