sf: spi_flash: use dma to copy data from mmap region if platform supports

Add dma memcpy api to the default spi_flash_copy_mmap(), so that
dma will be used to copy data when CONFIG_DMA is defined for the
platform.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jteki@openedev.com>

drivers/mtd/spi/spi_flash.c

@@ -16,6 +16,7 @@
 #include <spi.h>
 #include <spi_flash.h>
 #include <linux/log2.h>
+#include <dma.h>
 
 #include "sf_internal.h"
 
@@ -454,8 +455,16 @@ int spi_flash_read_common(struct spi_flash *flash, const u8 *cmd,
 	return ret;
 }
 
+/*
+ * TODO: remove the weak after all the other spi_flash_copy_mmap
+ * implementations removed from drivers
+ */
 void __weak spi_flash_copy_mmap(void *data, void *offset, size_t len)
 {
+#ifdef CONFIG_DMA
+	if (!dma_memcpy(data, offset, len))
+		return;
+#endif
 	memcpy(data, offset, len);
 }