rtl8xxxu: remove unused assignment value

at first, ret was assigned to zero, but later assigned to
a funciton,so the assignment to zero is no use, which can
simple be removed instead.

Signed-off-by: wengjianfeng <wengjianfeng@yulong.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210130072310.17252-1-samirweng1979@163.com