ZEN: Set CLEAN_MIN_KBYTES to 0

Per @hakavlad [1], enabling hard cache protection breaks i915.  Keep it
at zero so we don't run into the same issues previously reported.

[1] zen-kernel#218 (comment)

Signed-off-by: kernelOfTruth <kerneloftruth@gmail.com>

mm/Kconfig

@@ -142,7 +142,7 @@ config CLEAN_LOW_KBYTES
 config CLEAN_MIN_KBYTES
 	int "Default value for vm.clean_min_kbytes"
 	depends on SYSCTL
-	default "65536"
+	default "0"
 	help
 	  The vm.clean_min_kbytes sysctl knob provides *hard* protection
 	  of clean file pages. The clean file pages on the current node won't be