hw_random doc updates

Update documentation for the hw_random support to be current:

 - Documentation/hw_random.txt has been updated to reflect the
   current code:  it's a framework now, a "core" with a small
   sysfs interface, that hardware-specific drivers plug in to.
   Text specific to Intel hardware is now at the end.

 - Kconfig now references the Documentation/hw_random.txt file
   and better explains what this really does.

Both chunks of documentation now higlight the fact that the kernel entropy
pool is maintained by "rngd", and this driver has nothing directly to do with
that important task.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/hw_random/Kconfig

@@ -9,7 +9,14 @@ config HW_RANDOM
 	  Hardware Random Number Generator Core infrastructure.
 
 	  To compile this driver as a module, choose M here: the
-	  module will be called rng-core.
+	  module will be called rng-core.  This provides a device
+	  that's usually called /dev/hw_random, and which exposes one
+	  of possibly several hardware random number generators.
+
+	  These hardware random number generators do not feed directly
+	  into the kernel's random number generator.  That is usually
+	  handled by the "rngd" daemon.  Documentation/hw_random.txt
+	  has more information.
 
 	  If unsure, say Y.