os/bluestore: drop inline_dirty from struct ExtentMap

We don't need this member as we can simply clear inline_bl
to mark it as dirty.

Signed-off-by: xie xingguo <xie.xingguo@zte.com.cn>

src/os/bluestore/BlueStore.h

@@ -588,7 +588,6 @@ public:
     };
     vector<Shard> shards;    ///< shards
 
-    bool inline_dirty = false;
     bufferlist inline_bl;    ///< cached encoded map, if unsharded; empty=>dirty
 
     ExtentMap(Onode *o);