mtd: nand: qcom: enable BAM or ADM mode

1. DM_EN is only required for EBI2 NAND controller which uses ADM
2. BAM mode will be disabled after power on reset which needs to
   be enabled before starting any BAM transfers.

Reviewed-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>