RDMA/mlx5: Remove unused num_alloc_xa_entries variable

clang with W=1 reports
drivers/infiniband/hw/mlx5/devx.c:1996:6: error: variable
  'num_alloc_xa_entries' set but not used [-Werror,-Wunused-but-set-variable]
        int num_alloc_xa_entries = 0;
            ^
This variable is not used so remove it.
Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20230330153607.1838750-1-trix@redhat.comSigned-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/hw/mlx5/devx.c

@@ -1993,7 +1993,6 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT)(
 	int redirect_fd;
 	bool use_eventfd = false;
 	int num_events;
-	int num_alloc_xa_entries = 0;
 	u16 obj_type = 0;
 	u64 cookie = 0;
 	u32 obj_id = 0;
@@ -2075,7 +2074,6 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT)(
 		if (err)
 			goto err;
 
-		num_alloc_xa_entries++;
 		event_sub = kzalloc(sizeof(*event_sub), GFP_KERNEL);
 		if (!event_sub) {
 			err = -ENOMEM;