mtd: update description of MTD_BCM47XXSFLASH symbol

For years now we support writing to BCMA SoC serial flash, so don't
describe this driver as providing read-only support anymore.
Signed-off-by: NRafał Miłecki <zajec5@gmail.com>
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>

drivers/mtd/devices/Kconfig

@@ -113,12 +113,12 @@ config MTD_SST25L
 	  if you want to specify device partitioning.
 
 config MTD_BCM47XXSFLASH
-	tristate "R/O support for serial flash on BCMA bus"
+	tristate "Support for serial flash on BCMA bus"
 	depends on BCMA_SFLASH
 	help
 	  BCMA bus can have various flash memories attached, they are
 	  registered by bcma as platform devices. This enables driver for
-	  serial flash memories (only read-only mode is implemented).
+	  serial flash memories.
 
 config MTD_SLRAM
 	tristate "Uncached system RAM"