crush: include mapper.h in mapper.c

Include linux/crush/mapper.h in crush/mapper.c to get the prototypes of
crush_find_rule and crush_do_rule which are defined there. This fixes
the following GCC warnings when building with 'W=1':

  net/ceph/crush/mapper.c:40:5: warning: no previous prototype for ‘crush_find_rule’ [-Wmissing-prototypes]
  net/ceph/crush/mapper.c:793:5: warning: no previous prototype for ‘crush_do_rule’ [-Wmissing-prototypes]
Signed-off-by: NTobias Klauser <tklauser@distanz.ch>
[idryomov@gmail.com: corresponding !__KERNEL__ include]
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>

net/ceph/crush/mapper.c

@@ -17,10 +17,12 @@
 # include <linux/kernel.h>
 # include <linux/crush/crush.h>
 # include <linux/crush/hash.h>
+# include <linux/crush/mapper.h>
 #else
 # include "crush_compat.h"
 # include "crush.h"
 # include "hash.h"
+# include "mapper.h"
 #endif
 #include "crush_ln_table.h"