Staging: Use kcalloc or kzalloc

Use kcalloc or kzalloc rather than the combination of kmalloc and memset.

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

// <smpl>
@@
expression x,y,flags;
statement S;
type T;
@@

x =
-   kmalloc
+   kcalloc
           (
-           y * sizeof(T),
+           y, sizeof(T),
                flags);
 if (x == NULL) S
-memset(x, 0, y * sizeof(T));

@@
expression x,size,flags;
statement S;
@@

-x = kmalloc(size,flags);
+x = kzalloc(size,flags);
 if (x == NULL) S
-memset(x, 0, size);
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>