wifi: ath12k: fix VHT MCS assignment

While associating, firmware needs the peer's receive capability
to calculate its own VHT transmit MCS. Currently, the host
sends this information via mcs->rx_mcs_set field, but firmware
actually reads it from mcs->tx_mcs_set field. This mismatch is
incorrect.

This issue has not caused failures so far because most peers
advertise identical TX and RX capabilities. Fix this by
assigning the value to tx_mcs_set as expected.

Additionally, the rate control mask is intended to limit our
transmit MCS, so it should also apply to the peer's receive
capability. Update the logic accordingly.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1

Fixes: d8899132 ("wifi: ath12k: driver for Qualcomm Wi-Fi 7 devices")
Signed-off-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>
Signed-off-by: Pradeep Kumar Chitrapu <quic_pradeepc@quicinc.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Reviewed-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>
Link: https://patch.msgid.link/20251009211656.2386085-2-quic_pradeepc@quicinc.com


Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>