wifi: rtlwifi: Remove some exhalbtc deadcode

exhalbtc_rf_status_notify(), exhalbtc_coex_dm_switch() and
exhalbtc_antenna_detection() are unused since they were added in 2017's
commit 7937f02d ("rtlwifi: btcoex: hook external functions for newer
chips")

Remove them.

This leaves ex_btc8723b1ant_coex_dm_reset() unused.

Remove it.

exhalbtc_dbg_control(), exhalbtc_stack_update_profile_info(),
exhalbtc_set_hci_version(), and exhalbtc_set_bt_patch_version() are
unused since their addition in 2014 by
commit aa45a673 ("rtlwifi: btcoexist: Add new mini driver")

Remove them.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20241104144331.29262-1-linux@treblig.org