sfc: Update the description of SFC_MTD

SFC4000 boards also have an EEPROM exposed as MTD.
The boot configuration is accessed through MTD.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/Kconfig

@@ -16,9 +16,9 @@ config SFC_MTD
 	depends on SFC && MTD && !(SFC=y && MTD=m)
 	default y
 	---help---
-	  This exposes the on-board flash memory as MTD devices (e.g.
-	  /dev/mtd1).  This makes it possible to upload new firmware
-	  to the NIC.
+	  This exposes the on-board flash and/or EEPROM as MTD devices
+	  (e.g. /dev/mtd1).  This is required to update the firmware or
+	  the boot configuration under Linux.
 config SFC_MCDI_MON
 	bool "Solarflare SFC9000-family hwmon support"
 	depends on SFC && HWMON && !(SFC=y && HWMON=m)