ath10k: fix spelling mistake "montior" -> "monitor"

Trivial fix to spelling mistake in ath10k_warn message.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>