staging: lustre: mgc: Use !x to check for kzalloc failure

!x is more normal for kzalloc failure in the kernel.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression x;
statement S1, S2;
@@

x = kzalloc(...);
if (
- x == NULL
+ !x
 ) S1 else S2
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>