ubi: wl: Remove set but not used variable 'prev_e'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/mtd/ubi/wl.c: In function 'find_wl_entry':
drivers/mtd/ubi/wl.c:322:27: warning:
 variable 'prev_e' set but not used [-Wunused-but-set-variable]

It's not used any more now, so remove it.

Fixes: f9c34bb5 ("ubi: Fix producing anchor PEBs")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

drivers/mtd/ubi/wl.c

@@ -319,7 +319,7 @@ static struct ubi_wl_entry *find_wl_entry(struct ubi_device *ubi,
 					  struct rb_root *root, int diff)
 {
 	struct rb_node *p;
-	struct ubi_wl_entry *e, *prev_e = NULL;
+	struct ubi_wl_entry *e;
 	int max;
 
 	e = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
@@ -334,7 +334,6 @@ static struct ubi_wl_entry *find_wl_entry(struct ubi_device *ubi,
 			p = p->rb_left;
 		else {
 			p = p->rb_right;
-			prev_e = e;
 			e = e1;
 		}
 	}