mtd: nand: pxa3xx: Use info->use_dma to release DMA resources

In commit:

  commit 62e8b851
  Author: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
  Date:   Fri Oct 4 15:30:38 2013 -0300

  mtd: nand: pxa3xx: Allocate data buffer on detected flash size

the way the buffer is allocated was changed: the first READ_ID is issued
with a small kmalloc'ed buffer. Only once the flash page size is detected
the DMA buffers are allocated, and info->use_dma is set.

Currently, if the device detection fails, the driver checks the 'use_dma'
module parameter and tries to release unallocated DMA resources.

Fix this by checking the proper indicator of the DMA allocation, which
is 'info->use_dma'.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>