btrfs: scrub: remove redundant initialization of increment

increment is being initialized to map->stripe_len but this is never
read as increment is overwritten later on. Remove the redundant
initialization.

Cleans up the following clang-analyzer warning:

fs/btrfs/scrub.c:3193:6: warning: Value stored to 'increment' during its
initialization is never read [clang-analyzer-deadcode.DeadStores].
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/scrub.c

@@ -3190,7 +3190,7 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 	u64 generation;
 	int mirror_num;
 	struct btrfs_key key;
-	u64 increment = map->stripe_len;
+	u64 increment;
 	u64 offset;
 	u64 extent_logical;
 	u64 extent_physical;