wifi: rtw89: coex: translate slot ID to readable name

To analyze debug log quickly, use readable name in string format instead.

Signed-off-by: Ching-Te Ku <ku920601@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220920010939.12173-3-pkshih@realtek.com