rtlwifi: rtl8188ee: fix comparison pointer to bool warning in phy.c

Fixes coccicheck warning:

drivers/net/wireless/realtek/rtlwifi/rtl8188ee/phy.c:1584:14-18: 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/20200910135917.143723-2-zhengbin13@huawei.com