powerpc: Add missing prototype

Add one missing prototype for function rh_dump_blk. Fix warning treated as
error in W=1:

  arch/powerpc/lib/rheap.c:740:6: error: no previous prototype for ‘rh_dump_blk’ [-Werror=missing-prototypes]
Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/rheap.h

@@ -83,6 +83,9 @@ extern int rh_get_stats(rh_info_t * info, int what, int max_stats,
 /* Simple dump of remote heap info */
 extern void rh_dump(rh_info_t * info);
 
+/* Simple dump of remote info block */
+void rh_dump_blk(rh_info_t *info, rh_block_t *blk);
+
 /* Set owner of taken block */
 extern int rh_set_owner(rh_info_t * info, unsigned long start, const char *owner);