staging: iio: addac: Remove unnecessary else after return

This patch fixes the checkpatch warning that else is not generally
useful after a break or return.

This was done using Coccinelle:
@@
expression e2;
statement s1;
@@
if(e2) { ... return ...; }
-else
         s1
Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>