rtl8xxxu: remove set but not used variable 'rate_mask'

drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c:4484:6:
 warning: variable rate_mask set but not used [-Wunused-but-set-variable]

It is never used since commit a9bb0b515778 ("rtl8xxxu: Improve
TX performance of RTL8723BU on rtl8xxxu driver")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
1 file changed