libceph: don't set pages or bio in ceph_osdc_alloc_request()

Only one of the two callers of ceph_osdc_alloc_request() provides
page or bio data for its payload.  And essentially all that function
was doing with those arguments was assigning them to fields in the
osd request structure.

Simplify ceph_osdc_alloc_request() by having the caller take care of
making those assignments

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
index 6ddda5b..75f56d3 100644
--- a/include/linux/ceph/osd_client.h
+++ b/include/linux/ceph/osd_client.h
@@ -216,9 +216,7 @@
 					       struct ceph_snap_context *snapc,
 					       struct ceph_osd_req_op *ops,
 					       bool use_mempool,
-					       gfp_t gfp_flags,
-					       struct page **pages,
-					       struct bio *bio);
+					       gfp_t gfp_flags);
 
 extern void ceph_osdc_build_request(struct ceph_osd_request *req,
 				    u64 off, u64 len,