mm/zpool: update zswap to use zpool

Change zswap to use the zpool api instead of directly using zbud.  Add a
boot-time param to allow selecting which zpool implementation to use,
with zbud as the default.

Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Tested-by: Seth Jennings <sjennings@variantweb.net>
Cc: Weijie Yang <weijie.yang@samsung.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/Kconfig b/mm/Kconfig
index 12179b8..886db21 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -535,7 +535,7 @@
 	bool "Compressed cache for swap pages (EXPERIMENTAL)"
 	depends on FRONTSWAP && CRYPTO=y
 	select CRYPTO_LZO
-	select ZBUD
+	select ZPOOL
 	default n
 	help
 	  A lightweight compressed cache for swap pages.  It takes