rtlwifi: remove comparison of 0/1 to bool variable

The variable 'rtlpriv->rfkill.rfkill_state' is bool and can directly
assigned to bool values.

Fix the following coccicheck warning:

drivers/net/wireless/realtek/rtlwifi/core.c:1725:14-42: WARNING:
Comparison of 0/1 to bool variable

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200429140924.7750-1-yanaijie@huawei.com