P2P: Cleanup AP callbacks when removing the group

P2P: Cleanup AP callbacks when removing the group

Clear the P2P GO callback parameters when removing the group to avoid
using these for non-P2P AP mode.

This is a fix for the bug I found in the following scenario:

A) p2p_group_add
A) p2p_group_remove wlan0
A) add_n
A) set_n 0 ssid "testap"
A) set_n 0 key_mgmt NONE
A) set_n 0 mode 2
A) set_n 0 frequency 2412
A) enable_n 0

B) try connect to testap

Authentication request will be always rejected because of
HOSTAPD_ACL_REJECT and not cleaned callbacks when group removed.