rtlwifi: rtl8192ee: Remove set but not used variable 'err'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/realtek/rtlwifi/rtl8192ee/fw.c: In function rtl92ee_download_fw:
drivers/net/wireless/realtek/rtlwifi/rtl8192ee/fw.c:111:6: warning: variable err set but not used [-Wunused-but-set-variable]

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>