usb: chipidea: udc: compress return logic into line

Simplify return logic to avoid unnecessary variable assignment.

This issue was detected using Coccinelle and the following
semantic patch:

@@
local idexpression ret;
expression e;
@@

-ret =
+return
     e;
-return ret;

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>