powerpc: Remove configs/B4420QDS_NAND_defconfig board

DM_SPI and other driver model migration deadlines
are expired for this board.

Remove it.

Patch-cc: Ashish Kumar <ashish.kumar@nxp.com>
Patch-cc: Ruchika Gupta <ruchika.gupta@nxp.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
25 files changed