qcacld-3.0: Use mac_handle_t in wlan_hdd_subnet_detect

Change "qcacld-3.0: Introduce mac_handle_t" introduced a modern
name for what was previously called the tHalHandle. Transition
wlan_hdd_subnet_detect to use the new naming.

Change-Id: Idc648bd965dc29ed620bf8f85b04c7658e51253d
CRs-Fixed: 2262582
1 file changed