rtlwifi: btcoex: 23b 1ant: monitor bt is enabled or disabled

Check BT's status, and record it in field bt_disabled. When BT is disabled,
We do special action called wifi_only.  Also, we move the field from
'struct btc_coexist' to 'struct coex_sta_8723b_1ant'.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Yan-Hsuan Chuang <yhchuang@realtek.com>
Cc: Birming Chiu <birming@realtek.com>
Cc: Shaofu <shaofu@realtek.com>
Cc: Steven Ting <steventing@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>