wifi: ath12k: Avoid allocating rx_stats when ext_rx_stats is disabled

wifi: ath12k: Avoid allocating rx_stats when ext_rx_stats is disabled

Currently, driver allocates the struct ath12k_rx_peer_stats for each
station regardless of whether ext_rx_stats is enabled. This structure
is populated by the monitor destination ring for both single-user and
multi-user scenarios when ext_rx_stats is enabled. However, when
ext_rx_stats is disabled, this allocation is unnecessary and results in
additional memory consumption.

To address this issue, allocate the struct ath12k_rx_peer_stats only when
ext_rx_stats is enabled through debugfs. This change prevents unnecessary
memory allocation. Additionally, ensure that the station dump RSSI is
updated irrespective of the ext_rx_stats enablement.

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: P Praneesh <praneesh.p@oss.qualcomm.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20250409052647.81955-1-praneesh.p@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>