rtlwifi: btcoex: remove redundant initialization of variables ant_num and single_ant_path

The variables ant_num and single_ant_path are being initialized with a
value that is never read and are being updated later with a new value.
The initializations are redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200723163214.995226-1-colin.king@canonical.com