sfc: Expose flash region storing boot code as MTD

The boot code that appears as a PCI expansion ROM on the SFC4000 is
stored in flash.  Expose this as a standard MTD device to allow for
in-place upgrades.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/net/sfc/net_driver.h b/drivers/net/sfc/net_driver.h
index cdb11fa..c953eb1 100644
--- a/drivers/net/sfc/net_driver.h
+++ b/drivers/net/sfc/net_driver.h
@@ -655,6 +655,7 @@
  *	This field will be %NULL if no flash device is present.
  * @spi_eeprom: SPI EEPROM device
  *	This field will be %NULL if no EEPROM device is present.
+ * @spi_lock: SPI bus lock
  * @n_rx_nodesc_drop_cnt: RX no descriptor drop count
  * @nic_data: Hardware dependant state
  * @mac_lock: MAC access lock. Protects @port_enabled, @phy_mode,
@@ -731,6 +732,7 @@
 
 	struct efx_spi_device *spi_flash;
 	struct efx_spi_device *spi_eeprom;
+	struct mutex spi_lock;
 
 	unsigned n_rx_nodesc_drop_cnt;