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/include/spi_flash.h b/include/spi_flash.h
index 38587c2..91b43ee 100644
--- a/include/spi_flash.h
+++ b/include/spi_flash.h
@@ -42,6 +42,8 @@
 	u8		bank_read_cmd;
 	/* Bank write cmd */
 	u8		bank_write_cmd;
+	/* Current flash bank */
+	u8		bank_curr;
 
 	void *memory_map;	/* Address of read-only SPI flash access */
 	int		(*read)(struct spi_flash *flash, u32 offset,