mtd: nand: qpic-common: add defines for ECC_MODE values

Add defines for the values of the ECC_MODE field of the NAND_DEV0_ECC_CFG
register and change both the 'qcom-nandc' and 'spi-qpic-snand' drivers to
use those instead of magic numbers.

No functional changes. This is in preparation for adding 8 bit ECC strength
support for the 'spi-qpic-snand' driver.

Reviewed-by: Md Sadre Alam <quic_mdalam@quicinc.com>
Signed-off-by: Gabor Juhos <j4g8y7@gmail.com>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://patch.msgid.link/20250702-qpic-snand-8bit-ecc-v2-1-ae2c17a30bb7@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>