Update Readme.md

[brett8883]

dji_verify for P4P, P4 Standard, and P4 Advanced lives at /system/bin/dji_verify

For Mavic, Spark, and P4PV2 dji_verify lives in /sbin/dji_verify

We have successfully flashed a custom FC to a P4PV2 and the aircraft flies but still working on finding the right parameters to change.

Hope this is helpful