staging: lustre: libcfs: Use swap() in cfs_hash_bd_order()

Use swap() function instead of using a temporary variable for swapping
two variables.

The Coccinelle semantic patch used to make this change is as follows:
//<smpl>
@@
type T;
T a,b,c;
@@
- a = b;
- b = c;
- c = a;
+ swap(b, c);
//<smpl>

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>