fs/ext3/balloc.c: delete useless initialization

Delete nontrivial initialization that is immediately overwritten by the
result of an allocation function.

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

)

// <smpl>
@@
type T;
identifier i;
expression e;
@@

(
T i = \(0\|NULL\|ERR_PTR(...)\);
|
-T i = e;
+T i;
)
... when != i
i = \(kzalloc\|kcalloc\|kmalloc\)(...);

// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Jan Kara <jack@suse.cz>