mtd: spi-nand: macronix: Add a possible bitflip status flag

Macronix SPI-NANDs encode the ECC status into two bits. There are three
standard situations (no bitflip, bitflips, error), and an additional
possible situation which is only triggered when configuring the 0x10
configuration register, allowing to know, if there have been bitflips,
whether the maximum amount of bitflips was above a configurable
threshold or not. In all cases, for now, s this configuration register
is unset, it means the same as "there are bitflips".

This value is maybe standard, maybe not. For now, let's define it in the
Macronix driver, we can safely move it to a shared place later if that
is relevant.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240826101412.20644-9-miquel.raynal@bootlin.com