rsi: remove set but not used variables 'info, vif'

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

drivers/net/wireless/rsi/rsi_91x_main.c: In function 'rsi_prepare_skb':
drivers/net/wireless/rsi/rsi_91x_main.c:127:24: warning:
 variable 'vif' set but not used [-Wunused-but-set-variable]

drivers/net/wireless/rsi/rsi_91x_main.c:124:28: warning:
 variable 'info' set but not used [-Wunused-but-set-variable]

They're not used any more since 160ee2a1 ("rsi: fill rx_params only once.")

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