mtd: spi-nand: macronix: Extract the bitflip retrieval logic

mtd: spi-nand: macronix: Extract the bitflip retrieval logic

With GET_STATUS commands, SPI-NAND devices can tell the status of the
last read operation, in particular if there was:
- no bitflips
- corrected bitflips
- uncorrectable bitflips

The next step then to read an ECC status register and retrieve the
amount of bitflips, when relevant, if possible. The logic used here
works well for now, but will no longer apply to continuous reads. In
order to prepare the introduction of continuous reads, let's factorize
out the code that is specific to single-page reads.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240826101412.20644-8-miquel.raynal@bootlin.com