Staging: rtl8723au: core: Removed variable that is always 0.

The following patch removes a variable that is always 0 using
coccinelle.
The following semantic patch was used:

@@
identifier ret;
@@

-int ret = 0;
 ... when != ret
     when strict
-return ret;
+return 0;

Signed-off-by: Heena Sirwani <heenasirwani@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>