Tinker with the expression, see below:
Man Page for pcap-filter (all Section 7) - The UNIX and Linux Forums
type wlan_type subtype wlan_subtype
True if the IEEE 802.11 frame type matches the specified
wlan_type and frame subtype matches the specified wlan_subtype.
If the specified wlan_type is mgt, then valid wlan_subtypes are:
assoc-req, assoc-resp, reassoc-req, reassoc-resp, probe-req,
probe-resp, beacon, atim, disassoc, auth and deauth.