dt-bindings: net: wireless: ath10k: describe firmware-name property

For WCN3990 platforms we need to look for the platform / board specific
firmware-N.mbn file which corresponds to the wlanmdsp.mbn loaded to the
modem DSP via the TQFTPserv. Add firmware-name property describing this
classifier.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240306-wcn3990-firmware-path-v2-1-f89e98e71a57@linaro.org