mtd: gpmi: fix the bch setting backward compatible issue

Previous u-boot code changed the default bch setting behavior and caused
backward compatible issue. This fix choose the legacy bch geometry back
again as the default option. If the minimum ecc strength that NAND chips
required need to be chosen, it can be enabled by either adding DT flag
"fsl,use-minimum-ecc" or CONFIG_NAND_MXS_USE_MINIMUM_ECC in configs. The
unused flag "fsl,legacy-bch-geometry" get removed.

Fixes: 51cdf83e (mtd: gpmi: provide the option to use legacy bch geometry)
Fixes: 616f03da (mtd: gpmi: change the BCH layout setting for large oob NAND)
Tested-by: Tim Harvey <tharvey@gateworks.com>
Tested-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Han Xu <han.xu@nxp.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>