mtd: nand/fsmc: Add DMA support

The fsmc_nand driver uses cpu to read/write onto the device. This is inefficient
because of two reasons
- the cpu gets locked on AHB bus while reading from NAND
- the cpu is unnecessarily used when dma can do the job

This patch adds the support for accessing the device through DMA

Signed-off-by: Vipin Kumar <vipin.kumar@st.com>
Reviewed-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

include/linux/mtd/fsmc.h

@@ -172,6 +172,10 @@ struct fsmc_nand_platform_data {
 	enum access_mode	mode;
 
 	void			(*select_bank)(uint32_t bank, uint32_t busw);
+
+	/* priv structures for dma accesses */
+	void			*read_dma_priv;
+	void			*write_dma_priv;
 };
 
 extern int __init fsmc_nor_init(struct platform_device *pdev,