sf: Add bank address register writing support

This patch provides support to program a flash bank address
register.

extended/bank address register contains an information to access
the 4th byte addressing in 3-byte address mode.

reff' the spec for more details about bank addr register
in Page-63, Table 8.16
http://www.spansion.com/Support/Datasheets/S25FL128S_256S_00.pdf

Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mtd/spi/spi_flash.c b/drivers/mtd/spi/spi_flash.c
index 0e38f59..9ddd070 100644
--- a/drivers/mtd/spi/spi_flash.c
+++ b/drivers/mtd/spi/spi_flash.c
@@ -278,6 +278,32 @@
 	return 0;
 }
 
+int spi_flash_cmd_bankaddr_write(struct spi_flash *flash, u8 bank_sel)
+{
+	u8 cmd;
+	int ret;
+
+	ret = spi_flash_cmd_write_enable(flash);
+	if (ret < 0) {
+		debug("SF: enabling write failed\n");
+		return ret;
+	}
+
+	ret = spi_flash_cmd_write(flash->spi, &cmd, 1, &bank_sel, 1);
+	if (ret) {
+		debug("SF: fail to write bank addr register\n");
+		return ret;
+	}
+
+	ret = spi_flash_cmd_wait_ready(flash, SPI_FLASH_PROG_TIMEOUT);
+	if (ret < 0) {
+		debug("SF: write bank addr register timed out\n");
+		return ret;
+	}
+
+	return 0;
+}
+
 #ifdef CONFIG_OF_CONTROL
 int spi_flash_decode_fdt(const void *blob, struct spi_flash *flash)
 {