staging: lustre/lnet: Fix wrong typecasting warning generated by sparse

Fix the following warning generated about type casting by sparse

warning: cast removes address space of expression

The current implementation casts the structure pointers with (char *)
without __user annotation and then adds sizeof struct to it, thereby
generating the sparse warning. Fixed this by removing the unnecessary
char pointer type cast.

Signed-off-by: Niranjan Dighe <niranjan.dighe@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>