Staging: comedi: Move a dereference below a NULL test

If the NULL test is necessary, then the dereference should be moved below
the NULL test.

The semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/

).

// <smpl>
@disable is_null@
identifier f;
expression E;
identifier fld;
statement S;
@@

+ if (E == NULL) S
  f(...,E->fld,...);
- if (E == NULL) S

@@
identifier f;
expression E;
identifier fld;
statement S;
@@

+ if (!E) S
  f(...,E->fld,...);
- if (!E) S
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>