crush: include header for global symbols

Include the header to pickup the definitions of the global symbols.

Quiets the following sparse warnings:

warning: symbol 'crush_find_rule' was not declared. Should it be static?
warning: symbol 'crush_do_rule' was not declared. Should it be static?

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Sage Weil <sage@newdream.net>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ceph/crush/mapper.c b/net/ceph/crush/mapper.c
index 854ac53..363f8f7 100644
--- a/net/ceph/crush/mapper.c
+++ b/net/ceph/crush/mapper.c
@@ -20,6 +20,7 @@
 
 #include <linux/crush/crush.h>
 #include <linux/crush/hash.h>
+#include <linux/crush/mapper.h>
 
 /*
  * Implement the core CRUSH mapping algorithm.