remove mentionings of devfs in documentation

Now that devfs is removed, there's no longer any need to document how to
do this or that with devfs.

This patch includes some improvements by Joe Perches.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 422e31d..24ebd1c 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -207,8 +207,7 @@
 	  module will be called umem.
 
 	  The umem driver has not yet been allocated a MAJOR number, so
-	  one is chosen dynamically.  Use "devfs" or look in /proc/devices
-	  for the device number
+	  one is chosen dynamically.
 
 config BLK_DEV_UBD
 	bool "Virtual block device"