sf: Add memory mapped read support

Qspi controller can have a memory mapped port which can be used for
data read. Added support to enable memory mapped port read.

This patch enables the following:
- It enables exchange of memory map address between mtd and qspi
through the introduction of "memory_map" flag.
- Add support to communicate to the driver that memory mapped
 transfer is to be started through introduction of new flags like
"SPI_XFER_MEM_MAP" and "SPI_XFER_MEM_MAP_END".

This will enable the spi controller to do memory mapped configurations
if required.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
diff --git a/include/spi.h b/include/spi.h
index c44ebe8..c2086fc 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -27,6 +27,8 @@
 /* SPI transfer flags */
 #define SPI_XFER_BEGIN	0x01			/* Assert CS before transfer */
 #define SPI_XFER_END	0x02			/* Deassert CS after transfer */
+#define SPI_XFER_MMAP	0x08			/* Memory Mapped start */
+#define SPI_XFER_MMAP_END	0x10		/* Memory Mapped End */
 
 /* Header byte that marks the start of the message */
 #define SPI_PREAMBLE_END_BYTE		0xec
@@ -46,6 +48,7 @@
 	unsigned int bus;
 	unsigned int cs;
 	unsigned int max_write_size;
+	void *memory_map;
 };
 
 /**