wifi: ath12k: Decrease ath12k_sta_rc_update_wk() stack usage

wifi: ath12k: Decrease ath12k_sta_rc_update_wk() stack usage

Currently when building ath12k with llvm-18.1.7-x86_64 the following warning is
observed:

drivers/net/wireless/ath/ath12k/mac.c:4946:13: warning: stack frame size (1112) exceeds limit (1024) in 'ath12k_sta_rc_update_wk' [-Wframe-larger-than]

A major contributor to the stack usage in this function is:

        struct ath12k_wmi_peer_assoc_arg peer_arg;

Avoid the excess stack usage by dynamically allocating peer_arg
instead of declaring it on the stack.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00173-QCAHKSWPL_SILICONZ-1
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://patch.msgid.link/20241217202618.1329312-4-kvalo@kernel.org
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>