wifi: rtw88: coex: Use bitwise instead of arithmetic operator for flags

This silences the following coccinelle warning:
  WARNING: sum of probable bitmasks, consider |

Compile tested only.

Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/c68a8642c325f626ac34ccee71d9d9aa69f0c92c.1750733428.git.xiaopei01@kylinos.cn