Fix the following coccicheck warning:

drivers/net/wireless/intersil/orinoco/spectrum_cs.c:281:5-8: Unneeded
variable: "err". Return "0" on line 286
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200413082043.22468-1-yanaijie@huawei.com