bcache: drop "select CLOSURES"

The Kconfig entry for BCACHE selects CLOSURES. But there's no Kconfig
symbol CLOSURES. That symbol was used in development versions of bcache,
but was removed when the closures code was no longer provided as a
kernel library. It can safely be dropped.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>

drivers/md/bcache/Kconfig

 
 config BCACHE
 	tristate "Block device as cache"
-	select CLOSURES
 	---help---
 	Allows a block device to be used as cache for other devices; uses
 	a btree for indexing and the layout is optimized for SSDs.