mtd: nand: pxa3xx: Set info->use_dma properly

Currently, the variable info->use_dma is never set and always
zero-valued which means the driver never does DMA transfers.
We fix this by simply setting info->use_dma to the module parameter,
also named 'use_dma'. Note that the module parameter has the same name,
but different semantics.

This fixes a regression introduced by the below commit
which removed the info->use_dma variable set.

  commit 4eb2da89
  Author: Lei Wen <leiwen@marvell.com>
  Date:   Mon Feb 28 10:32:13 2011 +0800

      mtd: pxa3xx_nand: unify prepare command

Before the above commit, the driver had use_dma=1 on all NAND commands
except on CMD_STATUS. This behavior is long lost and we are not
recovering in this patch, either.

This was spotted and verified by human inspection.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Tested-by: Nikita Kiryanov <nikita@compulab.co.il>
Acked-by: Igor Grinberg <grinberg@compulab.co.il>
Reviewed-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>