mtd: spinand: Add support for XTX XT26G0xA

Add support for XTX Technology XT26G01AXXXXX, XTX26G02AXXXXX and
XTX26G04AXXXXX SPI NAND.

These are 3V, 1G/2G/4Gbit serial SLC NAND flash devices with on-die ECC
(8bit strength per 512bytes).

Tested on Teltonika RUTX10 flashed with OpenWrt.

Links:
  - http://www.xtxtech.com/download/?AId=225
  - https://datasheet.lcsc.com/szlcsc/2005251034_XTX-XT26G01AWSEGA_C558841.pdf


Signed-off-by: Felix Matouschek <felix@matouschek.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220418132803.664103-1-felix@matouschek.org