wifi: ath12k: use real noise floor instead of default value

ATH12K_DEFAULT_NOISE_FLOOR represents the approximate noise floor value
which is used for RSSI calculation. Commit "wifi: ath12k: handle WMI event
for real noise floor calculation" added support to get the real noise floor
value from the firmware. Add changes to use the real value now instead of
the default one.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.4.1-00199-QCAHKSWPL_SILICONZ-1

Signed-off-by: Raj Kumar Bhagat <quic_rajkbhag@quicinc.com>
Co-developed-by: Aditya Kumar Singh <aditya.kumar.singh@oss.qualcomm.com>
Signed-off-by: Aditya Kumar Singh <aditya.kumar.singh@oss.qualcomm.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20250623-support_real_noise_floor-v2-2-974bbafa317e@oss.qualcomm.com


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