rtlwifi: rtl8723ae: fix comparison pointer to bool warning in rf.c

Fixes coccicheck warning:

drivers/net/wireless/realtek/rtlwifi/rtl8723ae/rf.c:52:5-22: WARNING: Comparison to bool
drivers/net/wireless/realtek/rtlwifi/rtl8723ae/rf.c:482:6-14: WARNING: Comparison to bool

Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200910141642.127006-2-zhengbin13@huawei.com