Staging: comedi: drivers: Compressed two lines of code into one.

The following patch compresses two lines of code into one using
coccinelle and removes an unused variable.
The following semantic patch was used:

@@
expression ret;
identifier f;
@@

-ret =
+return
     f(...);
-return ret;

Signed-off-by: Heena Sirwani <heenasirwani@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>