nandbcb: fix the issue cannot support gf_14 NAND boot

bchtype in FCB should be associated to the gf_13/14 settings in BCH, fix
the issue and test on Micron 29F64G08CBABB, it can boot after the
change.

Signed-off-by: Han Xu <han.xu@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>