mtd: mtdblock: remove the needless mtdblks_lock

The global lock mtdblks_lock was used to protect the original mtdblks
array to avoid race conditions. As the mtdblks array was already gone,
but the mtdblks_lock is left, and it causes latency when open/release dev.
So we need to remove it here.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c
index 485ea75..bb4c14f 100644
--- a/drivers/mtd/mtdblock.c
+++ b/drivers/mtd/mtdblock.c
@@ -45,8 +45,6 @@
 	enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
 };
 
-static DEFINE_MUTEX(mtdblks_lock);
-
 /*
  * Cache stuff...
  *
@@ -286,10 +284,8 @@
 
 	pr_debug("mtdblock_open\n");
 
-	mutex_lock(&mtdblks_lock);
 	if (mtdblk->count) {
 		mtdblk->count++;
-		mutex_unlock(&mtdblks_lock);
 		return 0;
 	}
 
@@ -302,8 +298,6 @@
 		mtdblk->cache_data = NULL;
 	}
 
-	mutex_unlock(&mtdblks_lock);
-
 	pr_debug("ok\n");
 
 	return 0;
@@ -315,8 +309,6 @@
 
 	pr_debug("mtdblock_release\n");
 
-	mutex_lock(&mtdblks_lock);
-
 	mutex_lock(&mtdblk->cache_mutex);
 	write_cached_data(mtdblk);
 	mutex_unlock(&mtdblk->cache_mutex);
@@ -331,8 +323,6 @@
 		vfree(mtdblk->cache_data);
 	}
 
-	mutex_unlock(&mtdblks_lock);
-
 	pr_debug("ok\n");
 }