libceph: define ceph_decode_pgid() only once

There are two basically identical definitions of __decode_pgid()
in libceph, one in "net/ceph/osdmap.c" and the other in
"net/ceph/osd_client.c".  Get rid of both, and instead define
a single inline version in "include/linux/ceph/osdmap.h".

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/include/linux/ceph/osdmap.h b/include/linux/ceph/osdmap.h
index 167daf6..d05cc44 100644
--- a/include/linux/ceph/osdmap.h
+++ b/include/linux/ceph/osdmap.h
@@ -3,6 +3,7 @@
 
 #include <linux/rbtree.h>
 #include <linux/ceph/types.h>
+#include <linux/ceph/decode.h>
 #include <linux/ceph/ceph_fs.h>
 #include <linux/crush/crush.h>
 
@@ -119,6 +120,29 @@
 	return &map->osd_addr[osd];
 }
 
+static inline int ceph_decode_pgid(void **p, void *end, struct ceph_pg *pgid)
+{
+	__u8 version;
+
+	if (!ceph_has_room(p, end, 1 + 8 + 4 + 4)) {
+		pr_warning("incomplete pg encoding");
+
+		return -EINVAL;
+	}
+	version = ceph_decode_8(p);
+	if (version > 1) {
+		pr_warning("do not understand pg encoding %d > 1",
+			(int)version);
+		return -EINVAL;
+	}
+
+	pgid->pool = ceph_decode_64(p);
+	pgid->seed = ceph_decode_32(p);
+	*p += 4;	/* skip deprecated preferred value */
+
+	return 0;
+}
+
 extern struct ceph_osdmap *osdmap_decode(void **p, void *end);
 extern struct ceph_osdmap *osdmap_apply_incremental(void **p, void *end,
 					    struct ceph_osdmap *map,