staging: iio: compress return logic

Simplify function returns by merging assignment and return.
Found with Coccinelle.

Semantic patch:
@@
local idexpression ret;
expression e;
@@

-ret =
+return
     e;
-return ret;

Signed-off-by: Gargi Sharma <gs051095@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>