wifi: ath: create common testmode_i.h file for ath drivers

wifi: ath: create common testmode_i.h file for ath drivers

User space application requires that the testmode interface
is exactly same between ath drivers. Move testmode_i.h file
in ath directory to ensure that all ath driver uses same testmode
interface instead of duplicating testmode_i.h for each ath drivers.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.7.0.1-01744-QCAHKSWPL_SILICONZ-1
Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00173-QCAHKSWPL_SILICONZ-1

Signed-off-by: Aaradhana Sahu <quic_aarasahu@quicinc.com>
Reviewed-by: Aditya Kumar Singh <quic_adisi@quicinc.com>
Link: https://patch.msgid.link/20250119083657.1937557-2-quic_aarasahu@quicinc.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>