Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8723b1ant.c: In function btc8723b1ant_tdma_dur_adj_for_acl:
drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8723b1ant.c:1428:7: warning: variable wifi_busy set but not used [-Wunused-but-set-variable]
drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8723b1ant.c: In function btc8723b1ant_tdma_dur_adj_for_acl:
drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8723b1ant.c:1427:22: warning: variable bt_info_ext set but not used [-Wunused-but-set-variable]

'wifi_busy' is not used since commit 158707f9 ("rtlwifi:
btcoex: Restore 23b 1ant routine for tdma adjustment")

'bt_info_ext' is not used since commit 2622d7d8 ("rtlwifi:
btcoex: 23b 1ant: TDMA duration for ACL busy")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>