ath10k: remove not needed warning when peer unmap

Remove not needed warning when get peer unmap
event from the firmware. This is not critical
message. Instead print this as a debug message.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>