IB/mlx5: Delete locally redefined variable

Fix the following sparse warning:
drivers/infiniband/hw/mlx5/main.c:1061:29: warning: symbol 'pfn' shadows
an earlier one
drivers/infiniband/hw/mlx5/main.c:1030:21: originally declared here

Fixes: d69e3bcf ('IB/mlx5: Mmap the HCA's core clock register to user-space')
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mlx5/main.c

@@ -1057,9 +1057,6 @@ static int mlx5_ib_mmap(struct ib_ucontext *ibcontext, struct vm_area_struct *vm
 		return -ENOSYS;
 
 	case MLX5_IB_MMAP_CORE_CLOCK:
-	{
-		phys_addr_t pfn;
-
 		if (vma->vm_end - vma->vm_start != PAGE_SIZE)
 			return -EINVAL;
 
@@ -1082,7 +1079,6 @@ static int mlx5_ib_mmap(struct ib_ucontext *ibcontext, struct vm_area_struct *vm
 			    vma->vm_start,
 			    (unsigned long long)pfn << PAGE_SHIFT);
 		break;
-	}
 
 	default:
 		return -EINVAL;