staging: lustre: lnet: Replace sg++ with sg = sg_next(sg)

With scatterlist chaining, simply incrementing the array does not
work. sg_next macro was thus introduced to follow the chain links
when necessary. So replace sg++ with sg_next.

This change was made with the help of the following Coccinelle
semantic patch:
//<smpl>
@@
struct scatterlist *sg;
@@
-sg++
+sg = sg_next(sg)
//</smpl>

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