Make CONFIG_SLOW_WORK an automatic rather than manual config option

Make CONFIG_SLOW_WORK an automatic rather than manual config option so that
people configuring their kernels don't have to make the choice.  It can be
selected automatically by those things that require it (such as FS-Cache).

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Garzik <jgarzik@redhat.com>
Acked-by: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/Kconfig

@@ -1016,7 +1016,7 @@ source "arch/Kconfig"
 
 config SLOW_WORK
 	default n
-	bool "Enable slow work thread pool"
+	bool
 	help
 	  The slow work thread pool provides a number of dynamically allocated
 	  threads that can be used by the kernel to perform operations that
@@ -1026,6 +1026,8 @@ config SLOW_WORK
 	  by a series of mkdirs and a create call, all of which have to touch
 	  disk.
 
+	  See Documentation/slow-work.txt.
+
 endmenu		# General setup
 
 config HAVE_GENERIC_DMA_COHERENT