lib/Kconfig: make PRIME_NUMBERS not user selectable.

Linus doesn't like it user selectable, so kill it until
someone needs it for something else.
Signed-off-by: Dave Airlie <airlied@redhat.com>

lib/Kconfig

@@ -551,7 +551,7 @@ config SBITMAP
 	bool
 
 config PRIME_NUMBERS
-	tristate "Prime number generator"
+	tristate
 	default n
 	help
 	  Provides a helper module to generate prime numbers. Useful for writing