dimlib: make DIMLIB a hidden symbol

According to Tal Gilboa the only benefit from DIM comes from a driver
that uses it. So it doesn't make sense to make this symbol user visible,
instead all drivers that use it should select it (as is already the case
AFAICT).
Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

lib/Kconfig

@@ -555,8 +555,7 @@ config SIGNATURE
 	  Implementation is done using GnuPG MPI library
 
 config DIMLIB
-	bool "DIM library"
-	default y
+	bool
 	help
 	  Dynamic Interrupt Moderation library.
 	  Implements an algorithm for dynamically change CQ modertion values