sf: Read flash bank addr register at probe time

Read the flash bank addr register to get the state of bank in
a perticular flash. and also bank write happens only when there is
a change in bank selection from user.

bank read only valid for flashes which has > 16Mbytes those are
opearted in 3-byte addr mode, each bank occupies 16Mytes.

Suppose if the flash has 64Mbytes size consists of 4 banks like
bank0, bank1, bank2 and bank3.

Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mtd/spi/spi_flash_internal.h b/drivers/mtd/spi/spi_flash_internal.h
index db6c444..00ed1ee 100644
--- a/drivers/mtd/spi/spi_flash_internal.h
+++ b/drivers/mtd/spi/spi_flash_internal.h
@@ -28,6 +28,8 @@
 #define CMD_ERASE_64K			0xd8
 #define CMD_ERASE_CHIP			0xc7
 
+#define SPI_FLASH_16MB_BOUN		0x1000000
+
 /* Manufacture ID's */
 #define SPI_FLASH_SPANSION_IDCODE0	0x01
 #define SPI_FLASH_STMICRO_IDCODE0	0x20