FP4: Set BOOT_SECURITY_PATCH

* This is put in vbmeta, and Fairphone OS sets it

[merothh]:
- Set this to unbreak upgrade path for users on /dev ~t based off
  LineageOS trees to our forked tree.

Change-Id: I69485c8207eca5ee9e7f1f4e02d684707c6dece3