p2p: fix p2p configuration

The correct path should be under /data,
or it is not writable.

wpa_supplicant now support p2p overlay configuration, a unified
wpa_supplicant init entry can be used.

Bug: 238601241
Test: create a group and check this group is persisted
      after reboot
Change-Id: I803badb16c67aba741b0804485a714bd5b179223