rtlwifi: btcoex: Remove 21a 1ant configuration parameter

In file halbtc8821a1ant.c, there are directives that depend on an
undocumented configuration parameter BT_AUTO_REPORT_ONLY_8821A_1ANT
that cannot be set from Kconfig. This parameter is replaced by a
boolean in the main structure used by all routines. It still cannot
be changed dynamically, but it is easier to document.

Using a suggestion from Realtek, the auto report is turned on with this
patch.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Yan-Hsuan Chuang <yhchuang@realtek.com>
Cc: Pkshih <pkshih@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>