mtd: nand: raw: rockchip_nfc: add NAND_SKIP_BBTSCAN option

On Rockchip SoCs the first boot stages are written on NAND
with help of manufacturer software that uses a different format
then the MTD framework. Skip the automatic BBT scan with the
NAND_SKIP_BBTSCAN option to be able to pass the driver probe
function and to let the original data unchanged.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>