Renaming hash bucket locking functions

1. new abbreviated previx: ocf_hb (HB stands for hash bucket)
2. clear distinction between functions requiring caller to
   hold metadata shared global lock ("naked") vs the ones
   which acquire global lock on its own ("prot" for protected)
3. clear distinction between hash bucket locking functions
   accepting hash bucket id ("id"), core line and lba ("cline")
   and entire request ("req").

Resulting naming scheme:
ocf_hb_(id/cline/req)_(prot/naked)_(lock/unlock/trylock)_(rd/wr)

Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>

src/engine/engine_zero.c

@@ -23,12 +23,12 @@ static int ocf_zero_purge(struct ocf_request *req)
 	} else {
 		/* There are mapped cache line, need to remove them */
 
-		ocf_req_hash_lock_wr(req); /*- Metadata WR access ---------------*/
+		ocf_hb_req_prot_lock_wr(req); /*- Metadata WR access ---------------*/
 
 		/* Remove mapped cache lines from metadata */
 		ocf_purge_map_info(req);
 
-		ocf_req_hash_unlock_wr(req); /*- END Metadata WR access ---------*/
+		ocf_hb_req_prot_unlock_wr(req); /*- END Metadata WR access ---------*/
 	}
 
 	ocf_req_unlock_wr(req);