UBIFS: remove unnecessary code in ubifs_garbage_collect

In ubifs_garbage_collect,local variable "space_before" calculate twice. In
fact, at the beginning of the loop, there is no need to calculate this
variable. Calculate it before call "ubifs_garbage_collect_leb" is enough. This
patch just remove the unnecessary calculate code.
Signed-off-by: wang bo <wang.bo116@zte.com.cn>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

fs/ubifs/gc.c

@@ -668,8 +668,7 @@ int ubifs_garbage_collect(struct ubifs_info *c, int anyway)
 	ubifs_assert(!wbuf->used);
 
 	for (i = 0; ; i++) {
-		int space_before = c->leb_size - wbuf->offs - wbuf->used;
-		int space_after;
+		int space_before, space_after;
 
 		cond_resched();