wifi: ath12k: remove unused variable monitor_present

Variable monitor_present is not used yet and will not be used in future
monitor mode. So delete it as cleanup.

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3

Signed-off-by: Kang Yang <quic_kangyang@quicinc.com>
Link: https://patch.msgid.link/20241022110831.974-2-quic_kangyang@quicinc.com


Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>