rtlwifi: rtl8192c: fix comparison to bool warning in phy_common.c

Fixes coccicheck warning:

drivers/net/wireless/realtek/rtlwifi/rtl8192c/phy_common.c:1106:14-18: WARNING: Comparison to bool

Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200918102505.16036-3-zhengbin13@huawei.com